Wikipedia:Reference desk/Archives/Science/2015 August 15

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August 15

Interfere the gyroscope

Many of today's electronic toys are built-in with batteries. Even though we may turn them off, they can be made to monitor us in the dark.

Some sensors are easier to fool. You can use noise to against microphone, a steel box or Faraday cage to block radio. How do we disable the gyroscope without killing the toy?

Can we put the iPhone in a mechanical "cocktail shaker" to generate excessive G's to saturate the gyroscope's digital output?

Can we use vibration to induce wave inside the chip to make MEMS parts to oscillate to reduce the chip's precision?

Can we use external magnitic fields to induce currents inside analog circuits so they may generate errornous readings? -- Toytoy (talk) 14:29, 15 August 2015 (UTC)

You can exploit the practical limitations of the internal sensors in that manner - but without some knowledge of what those limits are (eg if you imagined that a mechanical gyro had perfect bearings) then you can't block them all. However, if you know the maximum rate at which the gyro can change direction, then exceed that rate - then you could certainly confuse it. Generating currents inside the phone to confuse analog circuits could very easily damage the phone though...so I don't recommend doing that unless you are VERY familiar with it's inner workings. SteveBaker (talk) 14:34, 15 August 2015 (UTC)

Why do you want to do this ? Your phone knowing which way is up is not what I would call an invasion of privacy. Merely pulling out the batteries is probably the safest way, but of course you need to put them back in to use the phone again. StuRat (talk) 14:37, 15 August 2015 (UTC)

Many phones (notably, Apple phones) have non-removable batteries. There have been instances of US terrorism investigators (and probably evil black-hat hackers) hacking into phones and loading software that prevents the OFF switch from turning the phone off, instead just making it look like it's been turned off, while the GPS, microphone and camera continue to provide data on what the bad guy is up to. So maybe you can't remove the batteries, and turning it off might not work. SteveBaker (talk) 14:47, 15 August 2015 (UTC)

I wouldn't trust any cell phone to really turn off when you hit the switch. By "non-removable batteries", what does that mean ? Can you just open up the case with a screwdriver to remove them, or are they actually soldered in ? What happens when the batteries go bad, you just need to replace the entire phone ? StuRat (talk) 16:07, 15 August 2015 (UTC)

It means the battery is not intended to be a user serviceable part. (In the time it took you to type that, you could have easily googled to see what's involved [1] ;) You can replace the battery, but it takes a few tools and some minor skills; most users will just take the iphone to the apple store or another service agent to have the battery serviced. SemanticMantis (talk) 20:56, 15 August 2015 (UTC)

It takes tools, time and certain expertise to change iPhone or many other Apple toys' batteries. This is not something you can do when you are on the road or somewhere where you want to completely turn off the phone.

Some other modern-day toys, such as Microsoft Surface and the Asus phone I am currently using also have non-serviceable batteries. In the Case of Surface 3 Pro, I was told battery removal can be very very nasty that you need to remove many glued and fragile parts to reach the battery. -- Toytoy (talk) 09:47, 16 August 2015 (UTC)

If you can't change the batteries, I'd consider the entire device to be disposable, and it better be priced accordingly. As for rechargeable battery life, I've been rather pleasantly surprised by my cell phones, where the batteries seem to last indefinitely, due to smart chargers. Not so for my walkie-talkies, portable DVD player, and laptop, where the batteries died after 2, 3, and 5 years, respectively. StuRat (talk) 15:19, 16 August 2015 (UTC)

Since many years ago, I always tape my laptop and cellphone's cameras PHYSICALLY. I always use an earphone "stud" (an earphone jack without the earphone) to plug the microphone jack (this still cannot disable the internal microphone though). There are always ways for hackers to abuse smart toys. -- Toytoy (talk) 15:06, 15 August 2015 (UTC)

I use the same trick with an earphone "stud", only on my PC. Seems to be the only way to mute it quickly. (It takes entirely too long to bring up the controls on the PC and mute it that way.) I leave it loosely inserted when not needed, so I only need to push it the rest of the way in to mute the PC. StuRat (talk) 20:07, 15 August 2015 (UTC)

My keyboard has a single dedicated key which can mute the volume. You could also make a simple keyboard shotcut to mute the audio. Of course if the task bar is visible, it should only take you about 5 seconds or so to mute the audio even without a simple keyboard shortcut, unless there's something seriously wrong with your computer, or your ability to use a mouse. Nil Einne (talk) 12:54, 17 August 2015 (UTC)

The problem is the system load is usually high when audio is on, like when playing a video. That makes it take something like 30 seconds to pop up the volume controls, during which time I would have to plug my ears to keep from being deafened. The earphone stud solves that problem nicely. (Yes, I could theoretically turn the volume down before playing the video, but since each video has a different volume level, it's difficult to know when I am about to play a loud one and be prepared for it.) StuRat (talk) 13:37, 17 August 2015 (UTC)

"unless there's something seriously wrong with your computer" - with any computer released in the past 6 years or so (and most computer released in the past 9 years or so), it shouldn't take you 30 seconds to open up the volume controls, except in real extreme circumstances like a multi threaded app running with real time priority (which playing videos should not be). If you're computer is still running Windows 9x, I guess this explains it, but for most people who aren't living in the less developed parts of the developing world, this isn't an issue. Nil Einne (talk) 00:36, 19 August 2015 (UTC)

If some hypothetical hacker has taken control of your computer to a sufficient degree to actually make use of the camera and microphone, then there are no software measures WHATEVER that'll protect you - muting the mic via some keyboard key only tells the OS to turn off the mic. It's easy to write hacks that'll turn it back on again. Black tape might be enough to effectively disable the camera (although some of cameras may be sensitive enough in low light conditions to pick up *some* light regardless) - but nothing short of disconnecting the wire to the microphone will work in that case. Some audio jacks physically switch the inbuilt microphone to an external mike - but others just tell the software to do the switch. Honestly, if you don't trust that you can keep hackers out of your computer - and you truly believe that the odds of you taking some loss as a result of that are significant - then you have a REAL problem. Once they're inside your machine, it's almost impossible not to give away everything of importance to you. It's naive to think that a strip of black tape and a dummy microphone plug will make a measurable improvement once you're hacked - and the bad guys have everything you type or click, everything you have online, every account detail. SteveBaker (talk) 22:51, 17 August 2015 (UTC)

Who said anything about mics? I was referring to StuRat's comment which I'm pretty sure was referring to the speakers. I agree that the button will only work, as long as the OS reacts to it (and this applies to both speakers and the mic), but with the vast majority of modern computers based on the Intel HD Audio standard (and this pretty much includes all AMD ones as well), there's no difference with plugging something in to one of the 3.5mm audio ports, since these basically just tell the OS to mute the speakers (or built in mic), if it's set up that way. In other words, it's a moot point and irrelevant to my reply which concerned whether or not StuRat's weird behaviour was necessary on any resonably recent computer (answer remains, it isn't, there are plenty of alternatives which would frankly be faster than what StuRat does if they weren't using a computer from 16 years ago or whatever). Nil Einne (talk) 00:39, 19 August 2015 (UTC)

battery removal

I remember being surprised to learn that one needed to "heat up the phone to soften the adhesive" to remove the batteries from certain models of cell phone from two cell phone manufacturers. StuRat in the "Interfere the gyroscope" section appears to be just as surprised as I was at how difficult it is to "merely pull out the battery".

They seem to be a rare exception -- practically all battery-powered devices I've seen make it fairly simple to pop out the batteries. (The phrase "tool-less battery" is mentioned in some Wikipedia articles in the context batteries that are especially easy to remove and replace; and many other articles mention the "battery compartment").

What Wikipedia article is a good place to describe battery compartments, techniques that try to prevent connecting the battery "backwards", and cite reliable sources who describe the relative ease or difficulty of replacing batteries? I imagine that article would go on to mention how the (physical) "grip" friction grooves or friction bumps on battery compartment lids inspired on-screen (virtual) "grab handle" icons. --DavidCary (talk) 16:39, 17 August 2015 (UTC)

Many of the most popular high end smart phones and tablets have batteries that aren't designed to be user replacable. i-devices back to the iPod are one obvious example, but so too the Nexus devices, the Galaxy S6. Even a number of ultrabook style laptops have non user replacable batteries, and some of the more mid range devices have also headed in that direction, e.g. the Moto G. Nil Einne (talk) 00:46, 19 August 2015 (UTC)

References

MEIOSIS

Re the entry for MEIOSIS: Does the "independent assortment" rule apply in MII aswell as in MI? In particular, in telophaseII, after the segregation of the sister chromatids (not necessarily identical because of cross-over), how are they allocated to the two poles of the 2 developing cells?```` — Preceding unsigned comment added by 45.47.137.105 (talk) 14:51, 15 August 2015 (UTC)

Explaining detail of homework question in physics

In the Fundamentals of Physics there is this problem: World's largest ball of string is about 2m in radius to the nearest order of magnitude. what is the total length of string in ball? The world’s largest ball of string is about 2 m in radius. To the nearest order of magnitude, what is the total length L of the string in the ball?

with following proposed solution:

Let us assume the ball is spherical with radius R = 2m. The string in the ball is not closely packed (there are uncountable gaps between adjacent sections of string). To allow for these gaps, let us somewhat overestimate the cross-sectional area of the string by assuming the cross section is square, with an edge length d = 4 mm. Then, with a cross-sectional area of d² and a length L, the string occupies a total volume of V = (cross-sectional area)(length) =d²L. This is approximately equal to the volume of the ball, given by ,(4/3)πr^3 which is about 4R^3 because p is about 3. Thus, we have d²L = 4R^3,

or

L = 4R^3/d² = 4(2m)^3/(4*10^(-3)m)² = 2 * 10^6m ≈10^6m ≈ 10^3km

I get that's only an approximation, Pi is treated as 3, for example. However, why is 2 * 10^6m ≈10^6m? Couldn't the answer just be 2000 km? --Scicurious (talk) 17:21, 15 August 2015 (UTC)

It's always good to do a sanity check. I have a 500 foot ball of string in my desk drawer (say 150 meters) - it's about 4" (10cm) in diameter. The volume of a sphere increases as the cube of the radius...so probably the length of the string increases by the cube of the radius. So my 10cm ball is 20 times smaller than your 2m ball...so I'd guess the length of string as 150x20x20x20m - which is 1,200 km...pretty amazingly close to your estimate of 2,000 km. So I think you're probably in the right ballpark. SteveBaker (talk) 17:49, 15 August 2015 (UTC)

True, but the OP has committed the cardinal error in exams and homework - failure to read the question. See Order of magnitude. 2000 km is the length to one significant figure, not to the nearest order of magnitude. (Incidentally, I'm assuming the question was originally - "... 2m in radius. To the nearest order of magnitude..." If it was punctuated exactly as the OP wrote it, the fault is with the examiner for not punctuating it correctly). Tevildo (talk) 18:38, 15 August 2015 (UTC)

Of course, we have an article - Biggest ball of twine - and the OP's numbers are about right. Its circumference is 12.62 m (which would correspond to a radius of almost exactly 2 m if it were spherical), and it's 2378 km long). Tevildo (talk) 19:34, 15 August 2015 (UTC)

Thanks for the link. The punctuation was wrong and I corrected the question.--Scicurious (talk) 19:47, 15 August 2015 (UTC)

Thinking a bit more about it, my 1,200km estimate is on the low side because there is a big empty region in the center of the ball of string on my desk...that void doesn't get scaled up when the ball gets bigger. It's easy to imagine that around half of the volume is empty in my 10cm ball. SteveBaker (talk) 22:43, 15 August 2015 (UTC)

Is this bad user interface design in a nuclear power plant?

I was reading this article about a British nuclear power plant. It shows pictures of the control room, which is a sea of buttons. Isn't it a bad idea to have so many buttons? Here is a picture of some mechanical valves. They look like a complicated mess, they don't appear to be in any sort of pattern. Is this bad user interface design? — Preceding unsigned comment added by 46.7.222.232 (talk) 17:30, 15 August 2015 (UTC)

Part of it is that if you didn't have a sea of buttons, but instead, some single controller of some kind - then you'd have introduced a single point of failure which could remove your ability to control absolutely everything! Having lots of simple buttons and switches does increase the probability of failure (more things that can go wrong) - but the consequence of a single failure isn't fatal because there are so many redundant ways to achieve the same results.

There have been cases of dramatically bad user interfacing though - one example was where a warning light had been tested and noted as a failure - so they tied a red tag to the light so people would know it had failed until someone could get around to replacing it. There was (of course) a backup signal light - but you couldn't see it because the red tag from the failed light covered it up! Another example (which is common in the airline industry too) is that of audio alarms...in many fault conditions, the number of alarms that go off at the same time makes for total cacophony - reducing the ability of operators to think calmly, and having the risk that important alarms get drowned out by a dozen unimportant alarms. Some systems gave you the ability to turn off the audio alarms - but then something VERY important could easily be missed. Being able to turn off the alarms individually solves that - but then you're left with people forgetting to turn them back on again.

Training is the key here - and having realistic simulators for these control consoles is a big part of that. SteveBaker (talk) 17:41, 15 August 2015 (UTC)

See also The Ethics of Madness. --Trovatore (talk) 22:43, 15 August 2015 (UTC)

Agreed. The word is redundancy. You want multiple alarms, all independent of each other, and multiple controls, also all independent of each other. And then you might even have alarms to tell you when one of the alarm systems fails an automated check. When dealing with an inherently dangerous technology, this level of redundancy is critical. StuRat (talk) 20:02, 15 August 2015 (UTC)

The fact that you do not understand what these buttons and valves are for, does not mean that they are "a complicated mess" or that "they don't appear to be in any sort of pattern". In fact controlling a nuclear power plant is not much different from controlling any other complex equipment like modern planes, for instance - they also have a lot of buttons. Ruslik_Zero 20:07, 15 August 2015 (UTC)

There can indeed be a problem with too many controls, where finding the one you want in a timely manner becomes difficult. I suppose PCs fall into that category, where finding the control to change a particular setting takes so long that most people don't bother. Of course, if they were well organized and had properly indexed help, then a lot more controls could be managed than if they are just randomly located. But, in a nuclear power plant, having all those valves remotely controlled from one well-organized control panel would have the downside of increasing the complexity of the system, and thus the vulnerability. StuRat (talk) 21:41, 15 August 2015 (UTC)

That's a good example though - people find it incredibly difficult to (say) change the resolution of their PC's display - but that's for two very good reasons:

1. They were never trained to do that...so they have to search for the solution rather than knowing how to do it in advance.
2. They don't do it very often...so even if they do figure out how to do it once, they'll forget how to do it a second time.

Neither of those things should be the case for nuclear reactor operators - firstly, they train all the time, and secondly, they have really high fidelity simulators that make sure that even infrequent ("once in a lifetime") emergency operations become commonplace because the simulator throws them up far more often than they happen in reality. SteveBaker (talk) 22:39, 15 August 2015 (UTC)

As for changing the PC screen resolution, I do it often, but it's not easy, as the exact sequence seems to change with each new version of Windows. In Windows 98 it was Start + Settings + Control Panel + Display + Screen Resolution tab, then Windows XP dropped the Settings level, then in Windows 7 it was Start + Control Panel + Adjust your computer's settings + Appearance and Personalization + Adjust screen resolution, then Windows 8 eliminated the Start button altogether, now God only knows where they've hidden it in Windows 10. But for things I do less often, like try to get Windows to display file extensions everywhere, I am lost. StuRat (talk) 14:58, 16 August 2015 (UTC)

On Windows 7, 10, and I presume 8 as well, right click on the desktop, and select screen resolution. MChesterMC (talk) 09:30, 17 August 2015 (UTC)

The alternative for making the majority of changes for the average user, which has pretty much been the same for Windows since Vista, continuining to 7, to 8 (with some minor complexities in 8) to 8.1 to 10, has been to access the Start menu or Start screen (e.g. with the start button) and simply type in what you want, e.g. "resolution" or "extensions" or "Control Panel". No need to worry about where it is. Of course if it's something that is handled via the the Control Panel, you can similarly just type "Resolution" or "extensions" in the search field, which AFAIK has also generally been the default active field when you open the Control Panel, so you can similarly just open the Control Panel and type. Since Vista, I've never understood why people waste their time hunting around in the Start menu/screen for stuff when they have a keyboard and acceptable typing skills. With the exception of very common stuff, which probably should be pinned to the task bar any way, most people are going to take longer to do so. Nil Einne (talk) 12:47, 17 August 2015 (UTC)

There you have to know the right keyword. For example, if I type in "file type" instead of "extensions" in Windows 7, it seems to take me to where I change the associations with each file type, rather than whether they are displayed or not. So, having to remember the magic keyword is as bad as having to remember the magic location. (I imagine there is also a magic keystroke, but with the same problem.) If you don't already know it, it can take a long time to find it. StuRat (talk) 13:52, 17 August 2015 (UTC)

One would assume, if you're the sort of person who needs to see the extension, you'd also know there's a difference between extensions and file types, but I guess there are always odd people. In any case, there's no magic word, as often of different words and combination of words which make sense will work for many things, and for most humans, the odd occasion they did choose a word which doesn't work, there's nothing stopping them realising they chose a dumb word. Like when they type File Type and from the description realise they were being dumb and actually what's to display the extension, not file type which is normally displayed by default in Explorer and is distinct from the extension. Nil Einne (talk) 00:53, 19 August 2015 (UTC)

I'd argue that the file extension should always be displayed, for every user, so you can never accidentally click on a executable you downloaded that's pretending to be something else. StuRat (talk) 00:15, 20 August 2015 (UTC)

Note the plant is Torness Nuclear Power Station, completed in 1980, sharing a design with Heysham nuclear power station; that article says that one was based on Hinkley Point B Nuclear Power Station, completed in 1967. Ideas of design then were different from now - that said, I shudder to think of some Apple-era nuke plant where you can't tell if you're turning the power on or off when you press on the little button, and all the other screens are frozen up. Hopefully that'll never happen. What's curious to me about the picture is that there seems to be some sort of metamerism between the stations, with repeated elements but slightly different set-ups at each one.

I always wanted to see "One Moment In Time" set to a China Syndrome like video with Whitney Houston frantically and futilely fooling around with such controls while the plant falls apart and radioactive smoke flies in the air, but I guess that ship has sailed also. Wnt (talk) 09:06, 16 August 2015 (UTC)

Yes, standardization between plants is also an issue, especially those owned by the same company, which presumably will occasionally transfer staff between them. For example, at a grocery chain I shop at (Meijer), each store has a completely different layout, even down to whether the door on the right is an entrance or exit, making it take twice as long to shop at a different location. I'd hate to think of that delay when a recently transferred nuclear power plant worker is trying to find an emergency shutoff valve. StuRat (talk) 15:06, 16 August 2015 (UTC)