TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）
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@Zecc … and how many compilers normalize the input?
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@dkf said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
The Saxons were a germanic people
Rather "germanized". Thanks DNA analyses, we now know that they are actually west slav, more related to czech and polish than german.
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@Bulb said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Zecc … and how many compilers normalize the input?
That's actually an interesting question to which I'd like to know the answer, if someone were to do the
.I guesstimate most will just throw a tantrum whenever they see "weird punctuation", unless we're talking about "exotic" functional languages letting you use funky characters for operators.
Other than that, I think most modern languages will accept letter and number characters in identifiers (plus underscore and maybe dashes), but I don't know (ᵒʳ ᵖᵃʳᵗᶦᶜᵘˡᵃʳˡʸ ᶜᵃʳᵉ ᵃᵇᵒᵘᵗ) any specifics.
Anyway, I just wanted an excuse to use ; in a post.
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Identifiers are normalized using Normalization Form C (NFC)
so at least some languages do. Also
Identifiers follow the specification in Unicode Standard Annex #31 for Unicode version 13.0
where that annex defines in a lot of words that only letters are allowed at the beginning (plus Rust adds
_) and then also digits are allowed plus_and a couple similar characters (plus Rust excludes the ill-fated zero-width joiner).All other sane languages use that annex #31 as base of their identifier syntax too.
… so a
;will be just an invalid character in most languages.
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@HardwareGeek said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Zecc Of course, a Greek question mark merely looks like a semicolon; it's an entirely different code point
And as you can imagine, that special code point has been deprecated years ago in favor of the regular semicolon.
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@Gąska Unicode occasionally has bouts of sanity, but it's still plagued by the mold of backward compati(de)bility.
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@Zerosquare The evil ideas thread is
.
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GitHub - reinderien/mimic: [ab]using Unicode to create tragedy
[ab]using Unicode to create tragedy. Contribute to reinderien/mimic development by creating an account on GitHub.
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TIL in Wisconsin, it's legal for 16 year olds to open carry a long semi-auto rifle, but not a nunchaku.
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@Gąska Nunchaku requires training to use
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@Applied-Mediocrity said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Gąska Nunchaku requires training to use
They can practice at school.
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@dkf said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
They can practice at school.
But they can't openly carry it there.
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@dkf said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Applied-Mediocrity said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Gąska Nunchaku requires training to use
They can practice at school.
Same with rifle
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TIL 1.f is not a valid literal in C#.
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jdk8u_nashorn/src/jdk/nashorn/internal/runtime/UnwarrantedOptimismException.java at master · JetBrains/jdk8u_nashorn
Contribute to JetBrains/jdk8u_nashorn development by creating an account on GitHub.
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TIL Master Chief is short for Master Chief Petty Officer, which is a pretty low rank considering all the things he's done. Someone in the command must hate him.
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@DogsB said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
jdk8u_nashorn/src/jdk/nashorn/internal/runtime/UnwarrantedOptimismException.java at master · JetBrains/jdk8u_nashorn
Contribute to JetBrains/jdk8u_nashorn development by creating an account on GitHub.
Seems like a pretty apt exception for a JavaScript engine.
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@Gąska said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
TIL Master Chief is short for Master Chief Petty Officer, which is a pretty low rank considering all the things he's done. Someone in the command must hate him.
Master chief petty officer is grade E-9, the highest enlisted (non-commissioned) rank in the Navy. (The designations Command master chief, Fleet/force master chief, Master Chief Petty Officer of the Navy, and Senior Enlisted Advisor to the Chairman are basically special appointments by a commanding officer, of the same rank as an ordinary master chief, and not necessarily something one can expect to be promoted into in the ordinary course of a career.) The master chief is the top expert in his field (e.g., damage control, hull maintenance, gunner's mate, quartermaster, etc.) on his/her ship or shore unit.
Edit: I a word.
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@HardwareGeek still, not making him an officer is a pretty dick move.
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@Gąska not really. A Master Chief is way better respected and actually has more influence at the tactical level than any officer. Tactical level officers are regarded as being fairly worthless, while a good NCO is worth their weight in gold and non commanding officers are trained to listen and take their advice really seriously. In most cases, they're the ones actually running things. The officers worry about broad strokes, the NCOs handle the execution.
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@Benjamin-Hall TIL as well I guess.
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@Gąska yeah. It's one of those military things. US doctrine gives lots of leeway to senior NCOs, especially in the Marines.
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Two other thoughts specific to Halo:
- "Real" officers of significant rank are generally not expected to run around in the thickest of combat. And the Master Chief needs significant rank (in his side, ie enlisted vs officer) to show that he's a long-time veteran of some of the nastiest fights. So if they made him a lieutenant or even Commander (using navy ranks, about the highest you could expect to do his job), he'd look really under-ranked.
- More importantly, the Spartans (especially his generation) were explicitly grunts. Disposable grunts. They didn't do strategy, they didn't command others (much), they weren't in the chain of command except as weapons. Told to go and fight and die. Giving him officer rank would muddy that message.
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@Benjamin-Hall Especially because, if he/she were to go to OCS and earn a commission, he/she'd be "promoted" to the lowest-ranking and least-respected of officer. Technically a promotion, but way less respect, if not also real authority.
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@HardwareGeek One flaw I do see in his rank is that if he really were a marine (rather than navy), he'd be a Master Gunnery Sergeant (aka Gunny), since Master Chief doesn't exist in that structure. And from what I read, those guys are way more respected. Basically mythical creatures that happen to actually walk around with normal mortals.
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@Benjamin-Hall I'm guessing this is about a game character. If so, I haven't played that game, so I'm not sure who we're talking about nor the in-game circumstances. I'm just basing my replies on real-world naval rates (ranks) and ratings (job specialties). And real-world master chiefs and master gunnery sergeants are long-term career military who know more about how the military really works than most officers, and certainly more than a still-wet-behind-the-ears ensign/2nd lieutenant.
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@HardwareGeek said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Benjamin-Hall I'm guessing this is about a game character. If so, I haven't played that game, so I'm not sure who we're talking about nor the in-game circumstances. I'm just basing my replies on real-world naval rates (ranks) and ratings (job specialties). And real-world master chiefs and master gunnery sergeants are long-term career military who know more about how the military really works than most officers, and certainly more than a still-wet-behind-the-ears ensign/2nd lieutenant.
Absolutely the game character. The character in question (Spartan 117, usually called Master Chief or Chief, protagonist of the Halo series) is basically an orbital drop space marine. Go down, kick alien butt (or human butt), sometimes fight on space ships. Always encased in a suit of power armor.
As it turns out, he's (one of?) the last of his generation of engineered super soldiers--kids taken, experimented on with augmentations and drugs, conditioned to be basically weapons. Take orders, kill who you're pointed at. So having him be an officer just doesn't fit at all.
But he's much more of a marine than a navy puke. And he's even in the marines (and fights alongside "real" marines all the time). So I'd say Gunny (Master Gunnery Sergeant) would fit better. Certainly not an officer rank.
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@Benjamin-Hall said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
So I'd say Gunny (Master Gunnery Sergeant) would fit better. Certainly not an officer rank.
It's the (imagined) future and in a military branch that doesn't exist at this point. You don't know what sort of rank title changes have been done in the interim. Assume E-9 or equivalent and stop worrying about it.
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@dkf said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Benjamin-Hall said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
So I'd say Gunny (Master Gunnery Sergeant) would fit better. Certainly not an officer rank.
It's the (imagined) future and in a military branch that doesn't exist at this point. You don't know what sort of rank title changes have been done in the interim. Assume E-9 or equivalent and stop worrying about it.
The word "Gunny" might have picked up some extremely inappropriate connotations by then.
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I kinda always knew file locking on Unix is a mess, but didn't realize how massive the mess is…
Jeremy Allison wrote in https://www.samba.org/samba/news/articles/low_point/tale_two_stds_os2.html:
What do you think the effect of this code on the lock created on the first file descriptor should be (so long as the close() call returns zero) ? If you answered "it should be silently removed when the second file descriptor was closed", congratulations, you have the same warped mind as the people who implemented the POSIX spec. Yes, that's correct. Any successful close() call on any file descriptor referencing a file with locks will drop all the locks on that file, even if they were obtained on another, still open, file descriptor.
Let me be clear to everyone: this behavior is never what you would want. Even experienced programmers are surprised by this behavior, because it makes no sense. Even after I've described this to Linux kernel hackers their response has been one of stunned silence, followed by a "but why would it do that"?
In order to discover if this functionality was actually correctly used by any application program or anything really depended on it, Andrew Tridgell, the original author of Samba once hacked the kernel on his Linux laptop to write a kernel debug message if ever this condition occurred. After a week of continuous use he found one message logged. When he investigated it turned out be be a bug in the "exportfs" NFS file exporting command, where a library routine was opening and closing the /etc/exports file that had been opened and locked by the main exportfs code. Obviously the authors didn't expect it to do that either.
The reason is historical and reflects a flaw in the POSIX standards process, in my opinion, one that hopefully won't be repeated in the future. I finally tracked down why this insane behavior was standardized by the POSIX committee by talking to long-time BSD hacker and POSIX standards committee member Kirk McKusick (he of the BSD daemon artwork). As he recalls, AT&T brought the current behavior to the standards committee as a proposal for byte-range locking, as this was how their current code implementation worked. The committee asked other ISVs if this was how locking should be done. The ISVs who cared about byte range locking were the large database vendors such as Oracle, Sybase and Informix (at the time). All of these companies did their own byte range locking within their own applications, none of them depended on or needed the underlying operating system to provide locking services for them. So their unanimous answer was "we don't care". In the absence of any strong negative feedback on a proposal, the committee added it "as-is", and took as the desired behavior the specifics of the first implementation, the brain-dead one from AT&T.
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On a more positive tune
… have to look at how it works.
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True, I used his tiktok.
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@Zecc said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
"Lord open my door"
Which religion is this? The Cult of Alexa?
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Michiel de Ruyter was a Dutch admiral during the 1600s. Widely regarded as one of the most skilled admirals in naval history, Dutch law requires there to always be a ship in the Royal Netherlands Navy bearing his name.
The Den Helder naval base has a WiFi network with the SSID "Michiel de Router".
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TIL about NASA's Jet Propulsion Laboratory's "lucky peanuts".
What Are JPL's Lucky Peanuts? - NASA Science
JPL's lucky peanuts are an unofficial tradition at big mission events.
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TIL the Tootsie Roll® candy was first manufactured in 1907. During the Korean War, in November 1950, UN troops (consisting mostly of US Marines) were surrounded and under attack at Chosin Reservoir in extremely cold weather. The UN troops used code words in radio communications, and their code word for 60 mm mortar ammunition was "tootsie roll". However, the USAF Far East Combat Cargo Command, which was dropping as much as 250 tons/day of supplies to the 30000 troops, did not understand their code word, and dropped literal Tootsie Roll® candy. They later figured it out and dropped mortar ammunition, but not before the Tootsie Rolls turned out to be a blessing in disguise.
Temperatures at the reservoir were estimated to be as low as -36 °F (-38 °C), and among many other problems this caused, all their rations were frozen and inedible. However, the candy could be put into a pocket or directly into the mouth, where body heat would soften it enough to be edible. For some time, the Tootsie Rolls were the only edible food they had and are credited by many survivors with saving their lives. They could also be warmed in a pocket for use as a makeshift putty that would quickly harden and freeze to effect temporary repairs on various sorts of equipment.
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TIL about Phistomefel's theorem. It's an advanced technique of solving sudoku. The theorem states that the 16 corner cells of the board (four 2x2 squares) have the exact same digits as the 16 cells around the central 3x3 square. It was named after some random guy on a German puzzle forum who posted about it last year and was apparently the first person in history to have noticed this.
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TIL the opening clarinet glissando at the start of Gershwin's Rhapsody in Blue was not written down by George Gershwin himself, at least not originally:
The distinctive glissando had been created quite by happenstance during rehearsals:
As a joke on Gershwin.... [Ross] Gorman [Whiteman's virtuoso clarinetist] played the opening measure with a noticeable glissando, 'stretching' the notes out and adding what he considered a jazzy, humorous touch to the passage. Reacting favorably to Gorman's whimsy, Gershwin asked him to perform the opening measure that way.... and to add as much of a 'wail' as possible.
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TIL that 5G cell phones and base stations operate at frequencies fairly close to those used by aviation radar altimeters. They're not really close, but due to the nature of RF filters, there's definitely overlap between the 5G frequencies and the frequencies that get through filters to the radar receivers' front-ends.
Radar altimeters are used for a variety of purposes and by a variety of aircraft. They are used by commercial airliners, as well as helicopters (e.g., medical evacuation) and general aviation (private and non-scheduled-passenger commercial) aircraft whose operators like and can afford high-end avionics. Most critically, they're used during approach and landing, and are especially important under low-visibility conditions. Radar altimeters are also the key component of TAWS, which is also a life-safety critical system.
The RTCA, which is "a not-for-profit corporation formed to advance the art and science of aviation and aviation electronic systems for the benefit of the public." Since the FAA is staffed largely by lawyers and bureaucrats, rather than engineers and pilots, they rely on RTCA for technical advice on avionics issues.
For their analysis, the use the actual approach to Chicago O'Hare Airport's runway 27L, the busiest runway at O'Hare (once the busiest airport in the world, now down to #4 in the US and #13 in the world, which is still really, really busy). They made the assumption that all existing 3G and 4G towers would be converted to 5G. They also analyzed the helicopter approaches to several large, urban hospitals.
I haven't read the entire 231-page report, and it's not entirely clear to me just who established it, but there is something called an interference tolerance mask (ITM) which is based on the worst-case analysis of real used by various types of aircraft. There are 3 ITMs based on the altimeters used by different classes (Category 1: commercial air transport (passenger and freight); Category 2: regional, business, and general aviation (GA); and Category 3: helicopters, both transport and GA). Spurious signals above this level may cause interference to some or all altimeters of the the class. The ICAO specifies a -6dB safety margin below the ITM.
They found that the 5G signals received by airline radar altimeter receivers would exceed the safety margin at several points during the approach to O'Hare, and actually exceed the ITM in two places, including just before landing at 200–300 feet AGL. The ITM for Category 2 altimeters is lower than Category 1, meaning they are more susceptible to interference, and the 5G signals would exceed the ITM for basically the entire approach, down to less than 200 feet AGL, resulting in a very high probability of interference.
Then there's the problem of idiots not putting their 5G phones into airplane mode while they're on the plane.
Edit: There was also high risk of interference to helicopters approaching and landing at urban hospitals.
Naturally, Verizon, AT&T, T-Mobile, et al., dispute the RTCA's findings. They are spending 10s of billions of dollars just to acquire the use of these frequencies, not to mention the rest of their 5G roll-out. They have orders of magnitude more money to spend to persuade the FCC to make these frequencies available to 5G than the RTCA, or even the FAA, have to persuade the FCC that this might not be a good idea. For the last few decades, the FCC has made frequency allocations by auctioning them to the highest bidder. The bidding for this auction starts at over $14.7B.
What will this ultimately mean for aviation safety?
But I'd guess it won't be FCC's top priority with that much money pushing the other way.Sauces:
https://www.youtube.com/watch?v=942KXXmMJdY Note: I assume Juan discusses the telecom industry's version of the story, but I haven't yet watched the video to that point. Edit: I just got to the beginning of that. He starts by saying that their white paper disputes the RTCA's findings, but as far as he can tell from the paper, they haven't done any actual testing themselves. "Trust us. Everything is going to be fine." Edit: Quotation from the industry's paper: "Furthermore, the FCC noted that they 'expect the aviation industry to take account of the RF environment that is evolving below the 3980 MHz band edge and take appropriate action, if necessary, to ensure protection of such devices.'" FCC, do better. You know that's not how this works. The new kid on the block (5G) has to accommodate the existing users (aviation) and not cause interference, especially when the existing use is life-safety-critical.
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@HardwareGeek said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
TIL that 5G cell phones and base stations operate at frequencies fairly close to those used by aviation radar altimeters. They're not really close, but due to the nature of RF filters, there's definitely overlap between the 5G frequencies and the frequencies that get through filters to the radar receivers' front-ends.
Radar altimeters are used for a variety of purposes and by a variety of aircraft. They are used by commercial airliners, as well as helicopters (e.g., medical evacuation) and general aviation (private and non-scheduled-passenger commercial) aircraft whose operators like and can afford high-end avionics. Most critically, they're used during approach and landing, and are especially important under low-visibility conditions. Radar altimeters are also the key component of TAWS, which is also a life-safety critical system.
The RTCA, which is "a not-for-profit corporation formed to advance the art and science of aviation and aviation electronic systems for the benefit of the public." Since the FAA is staffed largely by lawyers and bureaucrats, rather than engineers and pilots, they rely on RTCA for technical advice on avionics issues.
For their analysis, the use the actual approach to Chicago O'Hare Airport's runway 27L, the busiest runway at O'Hare (once the busiest airport in the world, now down to #4 in the US and #13 in the world, which is still really, really busy). They made the assumption that all existing 3G and 4G towers would be converted to 5G. They also analyzed the helicopter approaches to several large, urban hospitals.
I haven't read the entire 231-page report, and it's not entirely clear to me just who established it, but there is something called an interference tolerance mask (ITM) which is based on the worst-case analysis of real used by various types of aircraft. There are 3 ITMs based on the altimeters used by different classes (Category 1: commercial air transport (passenger and freight); Category 2: regional, business, and general aviation (GA); and Category 3: helicopters, both transport and GA). Spurious signals above this level may cause interference to some or all altimeters of the the class. The ICAO specifies a -6dB safety margin below the ITM.
They found that the 5G signals received by airline radar altimeter receivers would exceed the safety margin at several points during the approach to O'Hare, and actually exceed the ITM in two places, including just before landing at 200–300 feet AGL. The ITM for Category 2 altimeters is lower than Category 1, meaning they are more susceptible to interference, and the 5G signals would exceed the ITM for basically the entire approach, down to less than 200 feet AGL, resulting in a very high probability of interference.
Then there's the problem of idiots not putting their 5G phones into airplane mode while they're on the plane.
Edit: There was also high risk of interference to helicopters approaching and landing at urban hospitals.
Naturally, Verizon, AT&T, T-Mobile, et al., dispute the RTCA's findings. They are spending 10s of billions of dollars just to acquire the use of these frequencies, not to mention the rest of their 5G roll-out. They have orders of magnitude more money to spend to persuade the FCC to make these frequencies available to 5G than the RTCA, or even the FAA, have to persuade the FCC that this might not be a good idea. For the last few decades, the FCC has made frequency allocations by auctioning them to the highest bidder. The bidding for this auction starts at over $14.7B.
What will this ultimately mean for aviation safety?
But I'd guess it won't be FCC's top priority with that much money pushing the other way.Sauces:
https://www.youtube.com/watch?v=942KXXmMJdY Note: I assume Juan discusses the telecom industry's version of the story, but I haven't yet watched the video to that point. Edit: I just got to the beginning of that. He starts by saying that their white paper disputes the RTCA's findings, but as far as he can tell from the paper, they haven't done any actual testing themselves. "Trust us. Everything is going to be fine." Edit: Quotation from the industry's paper: "Furthermore, the FCC noted that they 'expect the aviation industry to take account of the RF environment that is evolving below the 3980 MHz band edge and take appropriate action, if necessary, to ensure protection of such devices.'" FCC, do better. You know that's not how this works. The new kid on the block (5G) has to accommodate the existing users (aviation) and not cause interference, especially when the existing use is life-safety-critical.
This is fascinating to me (NOT sarcastic). I don't understand a lot of it, nonetheless, interesting.
I've always wondered, if electronics (esp. phones) were really an issue they would have the flight attendants verify every phone was off, rather than just tell the passengers to turn them off. I can't imagine on any commercial flight there wasn't at least one passenger who didn't.
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@Karla said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
I've always wondered, if electronics (esp. phones) were really an issue they would have the flight attendants verify every phone was off, rather than just tell the passengers to turn them off. I can't imagine on any commercial flight there wasn't at least one passenger who didn't.
I think that, in general, there's unlikely to be a problem, but having everything off or in airplane mode makes it even more unlikely. Same with something like a GPS receiver; that's technically forbidden, too, but chance of it causing interference is extremely small.
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@HardwareGeek Too long; but did read.
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@Karla said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
I've always wondered, if electronics (esp. phones) were really an issue they would have the flight attendants verify every phone was off, rather than just tell the passengers to turn them off. I can't imagine on any commercial flight there wasn't at least one passenger who didn't.
It may have been in the very early days but the cockpits are all shielded against interference now. The main reason at this point is so that people aren’t fiddling with their gadgets during take off and landing so that if something goes wrong, they can get your attention more easily. (Those two periods are the main time things can go wrong.)
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@HardwareGeek said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
Same with something like a GPS receiver; that's technically forbidden, too, but chance of it causing interference is extremely small.
I don't think receiver is forbidden. Pilots even use them themselves during operation, in company applications on company iPads (Juan showed some applications recently, and e.g. the airport chart clearly used the iPad's GPS to show the position).
@Arantor said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
It may have been in the very early days but the cockpits are all shielded against interference now.
The avionics is well shielded now, but something could still be induced into the various antennas. Fortunately there is a layer of metal between the phones and the antennas on the outside, so the risk is low.
This radar altimeter issue is more serious because the source of the interference is on the outside, and because the operating principle makes them more susceptible.
The principle is explained somewhere in that report (and shown in the video). The radar sends out chirps of linearly increasing carrier frequency and senses the difference in frequency of the return (which indicates the time it took for it to come back, but apparently it is more accurate that way). But that means it needs to receive a wide band instead of just single tuned frequency, and that makes it harder to filter out frequencies outside the intended range.
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@Arantor said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
@Karla said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
I've always wondered, if electronics (esp. phones) were really an issue they would have the flight attendants verify every phone was off, rather than just tell the passengers to turn them off. I can't imagine on any commercial flight there wasn't at least one passenger who didn't.
It may have been in the very early days but the cockpits are all shielded against interference now. The main reason at this point is so that people aren’t fiddling with their gadgets during take off and landing so that if something goes wrong, they can get your attention more easily. (Those two periods are the main time things can go wrong.)
I think it's more a public perception thing. People don't understand how things work, so they freak out about nothing. Phones use mysterious waves, like you know, microwaves. And you heard those interference sounds in loudspeakers caused by phones, right? So surely a phone can bring down a plane, it's just science.
It's easier to introduce a useless safety rule than to deal with panicking people all the time. See also: 'no phones' signs at gas stations.
I know someone who always turns off her phone during thunderstorm. She panicks every time I talk on the phone during one.
: Turn it off! It's so risky! You'll get struck by a lightning!
: How the fuck would that even work?
: You know... waves!
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@Bulb said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
I don't think receiver is forbidden.
Some receivers definitely are. Most receivers are also unintentional transmitters and have at least some (possibly very small) potential to cause interference with some (not necessarily aviation) other receiver.
Most receivers contain a local oscillator (LO) which is mixed with the incoming RF from the antenna to produce sum and difference frequencies (RF + LO and abs(RF - LO)). Usually the receiver is tuned by changing the LO frequency so that the sum (or difference) frequency is a fixed-by-design intermediate frequency (IF), which is then filtered to remove undesired frequencies, then amplified and demodulated. It is far easier and more effective to design a filter to select the desired receive signal and remove other signals on nearby frequencies for a fixed IF than to make that filter tunable for the original RF signals. (It's not impossible. It's called a direct conversion receiver, and until Edwin Armstrong and/or Lucien Lévy invented the superheterodyne receiver, all radio receivers were built that way. According to one source I read, most cell phone receivers are direct conversion.)
Unless the receiver is exceptionally well shielded, some of the LO and/or IF frequency signals in the receiver can radiate unintentionally. Depending on the LO and IF frequencies, this leakage can cause problems. In particular, the IF used by the once-ubiquitous FM broadcast receiver is typically in the aviation band, and has serious potential for interference. (Stories exist of shipwrecked sailors/downed aviators taking their FM radio and hacking it slightly to produce a Morse code transmitter in the aviation band to signal search and rescue planes. The trouble with this is it's on a frequency (navigation aid) aviators don't typically actually listen to, so they have to searching with the knowledge that someone might be transmitting a distress signal on that frequency; a random plane passing nearby won't notice it.) These are, AFAIK, universally banned on aircraft, and will probably remain banned forever, even after FM radio disappears under the onslaught of digital broadcast services, as happened to analog TV.
Anyway,
Pilots even use them themselves during operation, in company applications on company iPads (Juan showed some applications recently, and e.g. the airport chart clearly used the iPad's GPS to show the position).
With some exceptions (most notably, cell phones), an aircraft operator can authorize the use of some or all personal electronic devices (PEDs) during some or all phases of flight. Obviously, the company iPads running company apps are authorized by the company. But even company iPads running company apps are forbidden to the flight crew by the FAA during takeoff and landing if they're also running non-FAA-approved apps. (Pilots are allowed to use PEDs as "electronic flight bags" (EFBs), replacing the paper charts and manuals they would otherwise carry, including things they might need to reference during approach and landing. However, the EFB apps must be FAA-approved; otherwise, they're forbidden during critical phases of flight.)
Passengers PEDs may be approved at the discretion of the operator, if the operator has determined they're safe. (Generally, for commercial flights, this means the airline, not the pilot. Even if the PIC has the legal authority to authorize a PED — which is unclear to me, since AIUI it requires actually testing the device, or at least devices of that type — aboard his/her flight, since he/she is ultimately responsible for the safety of flight, a pilot who doesn't follow his/her employer's policies is very likely to no longer have an employer.) So what is allowed may vary by airline and type of aircraft. One of the sources I found is about 15 years old, so thing may have changed since, but at that time one and only one major US airline allowed GPS receivers to be operated aboard their aircraft. It is also possible that a device has been determined to be safe for operation by the crew in the cockpit but may be either unsafe or inadequately tested for use in the cabin by passengers.
Of course, many if not all of you are familiar with varying restrictions based on the phase of the flight. Some devices are allowed during cruise but not during takeoff and landing. This may be for a combination of reasons: Distracting passengers during safety instructions. Clutter in the way of an emergency evacuation. And the possibility of RF interference is a little more critical when you're 100 feet off the ground than when you're 30000 feet off the ground.
Cell phones are an exception. Their use is forbidden while airborne, in any aircraft, commercial or private, by the FCC. In an aircraft on the ground is fine (if permitted by the operator), but airborne is always prohibited. It probably won't work well, if at all, anyway; cell tower antennas are designed to "look" at the ground, not up in the sky. And if it does work, it's fairly likely to cause problems with the cell network. Sitting in your bedroom, only a few nearby cell towers (if any;
T-Mobile) can "hear" your phone. Airborne, hundreds of towers may be able to "hear" it, and towers farther away may be able to "hear" it better (because of the angle to the antenna) than nearby towers; the network isn't designed for that use case. Some airlines offer cell phone use through an on-board cell base station (relayed either through a satellite or directly to the ground); this must be disabled when entering US airspace, due to the FCC restriction.
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@HardwareGeek said in TIL （ａｂｏｕｔ ｔｈｅ Ｄａｒｋ Ａｒｔｓ ｏｆ ＨＴＭＬ）:
Cell phones are an exception. Their use is forbidden while airborne, in any aircraft, commercial or private, by the FCC.
The FAA, however, does not make any such statements and actually leaves it up to the operator of the aircraft in question.
The FCC's ruling seems to be more about the potential disruption to the ground network rather than connected to potential problems with the airplane.
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@Rhywden Yes.
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@HardwareGeek I've heard cell phones can get pretty shouty if they can't find a cell tower to connect to. So why not install a 'fake' cell tower in the plane which just quiety tells all cell phones 'You're in an aircraft. Shut up.'
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