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March 16

Why do I get all sweaty when I pull an all-nighter?

Just last night I stayed up all night to get some work done. Shower in the morning so I'm nice and clean, get changed into new clothes, then not ninety minutes later I'm sweating like a pig. Staying up all night isn't something I do super-frequently, but getting all sweaty happens every time I do. --2404:2000:2000:5:0:0:0:C2 (talk) 00:55, 16 March 2015 (UTC)[reply]

We can't answer medical questions. If you think your body is misbehaving, either on its own or because you did something to it unwisely, you should seek the advice of someone with proper training. --Jayron 32 01:43, 16 March 2015 (UTC)[reply]

That is called a night sweat and it can mean many things. Bubba73 ^{You talkin' to me?} 02:01, 16 March 2015 (UTC)[reply]

Night sweat is not relevant, and User:Kainaw/Kainaw's criterion applies, the OP has asked for a personal diagnosis. μηδείς (talk) 03:04, 16 March 2015 (UTC)[reply]

I disagree, the question closest in format to mine is the "white painful bumps" one. Please interpret my question in the light of that:

I sometimes get white painful bumps on my tongue. Is that a side-effect of tooth whitening toothpaste?

It is apparent that the questioner is asking if his or her white bumps are caused by the toothpaste, but that is not the literal question. The literal question is asking if the toothpaste has been known to have a side-effect of causing white bumps. This may be answered as long as care is taken not to diagnose what the questioner's white bumps are.

--2404:2000:2000:5:0:0:0:C2 (talk) 03:11, 16 March 2015 (UTC)[reply]

I don't know the answer to your question, but I can confirm that you are not alone in this experience. If I am working overnight, I find that there are moments at which I get extremely sweaty (and feel surprisingly hot, given that it's the middle of the night and the central heating is turned off), and once or twice this has carried over into the following morning. I'd be interested to know what causes this. RomanSpa (talk) 04:07, 16 March 2015 (UTC)[reply]

One possible reason is just that your antiperspirant has worn off. This doesn't have anything to do with the time of day, other than, if you apply antiperspirant in the morning as most people do, then late at night is when it is likely to wear off.

Also, do you use caffeine to stay awake ? This can cause sweating: [1]. StuRat (talk) 05:30, 16 March 2015 (UTC)[reply]

Personally I agree with μηδείς/Jayron32. But anyway some people seem to have failed to read the question. The OP didn't say anything clearly about sweating at night when you stay up late. They said they sweated a lot the morning after they stayed up late. The question is somewhat ambigious, it's possible they also sweat a lot while staying up, but this wasn't clearly stated. Nil Einne (talk) 07:30, 16 March 2015 (UTC)[reply]

What is clear is that the IP is wikilawyering (Every single clause has the word I in it, it's not a general question) and those offering answers haven't comprehended the question as stated. This should be shut down, since we have no idea, maybe the OP is diabetic, or has a heart condition. If it's serious enough to need answering it's serious enough to take to his gen prac. μηδείς (talk) 22:20, 16 March 2015 (UTC)[reply]

Thawing a solution/emulsion and homogeneity

If I thaw a solution (maybe containing reagents) or milk, am I right in thinking that I need to wait for the whole lot to melt and then mix to ensure that I remove a proper (i.e. containing the correct ratios of constituents) aliquot? I imagine it might depend on the precise contents. I'm interested in reagents (used in life sciences) in general and milk specifically (which I sometimes freeze domestically for convenience). --92.6.114.195 (talk) 08:43, 16 March 2015 (UTC)[reply]

Correct, you should always thaw the whole solution to ensure homogeneity. If not, you may suffer from the reverse of fractional freezing or temperature dependant solubility issues. 131.251.254.154 (talk) 09:38, 16 March 2015 (UTC)[reply]

In the case of milk, freezing can cause lipids to clump together, so you get "cream on the top". Rehomogenization would then be required to get it back to the original mixed state. StuRat (talk) 16:51, 16 March 2015 (UTC)[reply]

The worlds of nature which was building on superconductivity

1) Did micro-nano worlds build on superconductivity?

2) Did a world of biological cells build on the superconductivity?--85.141.236.250 (talk) 13:45, 16 March 2015 (UTC)[reply]

I'm not sure what the OP means but I interpret as a question that I've wondered about for a while. Do individual molecules exhibit superconductivity at higher temperatures? For example, if you knock an electron out of a benzene ring or larger aromatic system and use some applied field to start the hole moving around the ring with a measurable speed (because of resonance I'm not sure you can actually do this, but then again, I'm not sure you can't provided you can measure the momentum to narrow the range of available states...), will it maintain that speed under another force is applied? Wnt (talk) 14:04, 16 March 2015 (UTC)[reply]

To my knowledge superconductors have never existed on Earth, until humans made some, relatively recently. So "no" to both of your questions. Covellite is often suggested as a "naturally occurring superconductor", but I don't think it would act as a super conductor under any Earth-normal conditions. SemanticMantis (talk) 14:13, 16 March 2015 (UTC)[reply]

B-birds

Hi everyone, I'm looking for help identifying these birds. Although they were at the zoo, they were not in individual enclosures and thus not identified. — Crisco 1492 (talk) 15:44, 16 March 2015 (UTC)[reply]

Species found in Gembira Loka
Crested serpent eagle
Black lory
A female eclectus parrot
Dusky lory

The red and blue one looks a lot like a female eclectus parrot. By the way, I just used google's reverse image search, and clicked through a few similar examples until I found one that seemed to be the same bird and have a good description. It's a fun game; no bird expertise needed to at least suggest candidates. SemanticMantis (talk) 18:41, 16 March 2015 (UTC)[reply]

The bird is most definitely a female eclectus. My friend owns one that looks exactly like this one, and she loves to be rubbed and handled by me. :-) --Modocc (talk) 18:57, 16 March 2015 (UTC)[reply]

Does the parrot get jealous of you rubbing and handling your friend? :) μηδείς (talk) 22:13, 16 March 2015 (UTC)[reply]

The last one could be Dusky lory. The geography, beak/eyes/legs colors match; plumage is close. Your bird looks thinner/bigger to me, but that could be just a matter of perspective. Abecedare (talk) 21:58, 16 March 2015 (UTC)[reply]

And the pair in the second photograph is likely to be that of Black lories (see similar photo here, and description here). The bird in the first photograph will be difficult to identify given the tight view, but may be someone more knowledgeable will pipe in. Abecedare (talk) 22:35, 16 March 2015 (UTC)[reply]

Thanks, everyone! I'll update the image pages on Commons. My apologies for regularly (well, irregularly) asking here, but I know that there are people who know birds well and would have a much easier time getting the right species than me and Google. — Crisco 1492 (talk) 23:50, 16 March 2015 (UTC)[reply]

Your questions are well-directed at the ref-desk, since one of its purpose is to help improve wikipedia content, which your photographs combined with species identification certainly do. Plus they are fun to sleuth... so keep them coming. Cheers. Abecedare (talk) 00:46, 17 March 2015 (UTC)[reply]

Bird number 1 appears to be the crested serpent eagle, Spilornis cheela. μηδείς (talk) 01:24, 17 March 2015 (UTC)[reply]

- I think I remember seeing such a label around this one. Thanks! — Crisco 1492 (talk) 01:33, 17 March 2015 (UTC)[reply]

Nice find, Medeis. Abecedare (talk) 01:54, 17 March 2015 (UTC)[reply]

I used the same reverse-image method (which I have used before, but not exclusively) and the picture I found was a few page scrolls down. Taxonomy has always been a hobby of mine, and it was easy to quickly rule out most of the other pictures. The difficult part is that the crested serpent eagle is highly variable. μηδείς (talk) 16:54, 17 March 2015 (UTC)[reply]

I agree with Abecedare, Crisco 1492, please post more, this is both beautiful and fun. μηδείς (talk) 17:19, 19 March 2015 (UTC)[reply]

- I'll see what I can find on my next photography trip! Shame I lack the equipment for most wild birds. — Crisco 1492 (talk) 23:08, 19 March 2015 (UTC)[reply]

One can find a lot of wild birds in singles' bars, but the environs are not well lit, and photography may be discouraged. In any case, with a little knowledge of taxonomy and google images, it's amazing what you can do. Back in the early years BS (Before Simpsons) none of this was imaginable. μηδείς (talk) 05:38, 20 March 2015 (UTC)[reply]

How was the speed of quantum entanglement measured?

In some experiment, the speed of the effects of quantum entanglement was estimated to be $10000c+$ . How was this accomplished if no information can be transmitted at a speed faster than light? — Melab±1 ☎ 16:20, 16 March 2015 (UTC)[reply]

Is your question "how was it measured?" or "how does a faster-than-light effect work?" If it's the former, that's simple: you compare clocks after the fact, which does not rely on real-time data transmission and so doesn't care about the speed of light. If it's the latter, then the answer is far more complicated, but quantum entanglement, the no-communication theorem, and the EPR paradox (a famous objection to entanglement) may provide a good start. The short version is that events can propagate FTL without usable information being transmitted with them (or without even the capability for information transfer existing). — Lomn 17:29, 16 March 2015 (UTC)[reply]

The paper is arXiv:1303.0614. I guess the idea is that if you generate a Bell pair and send the halves in opposite directions to detectors a distance d apart, and in front of the detectors are polarizers that rotate randomly at a time scale comparable to d/10000c, and you observe a violation of Bell's inequality in that experiment, then you've established a lower bound of around 10000c on some quantity. Calling that quantity the "speed of entanglement" is misleading since entanglement doesn't and couldn't have a speed. What they're really bounding is the signaling speed of some unspecified classical hidden-variable theory that uses superluminal signaling to (imprecisely) simulate entanglement. -- BenRG (talk) 00:19, 17 March 2015 (UTC)[reply]

light move back and forverd in time , in high dimension , so its transfer statistic information in this dimension that can be seen from entanglement , thanks water nosfim — Preceding unsigned comment added by 192.116.142.154 (talk) 10:58, 17 March 2015 (UTC)[reply]

Is it possible computer’s programming of the biological cells (gene or genome)?

Is it possible to over completed the biological (natural) program code of the biological cells (gene or genome) by computer’s logical software code? I saw some interesting films in which it is been done.--83.237.194.120 (talk) 16:33, 16 March 2015 (UTC)[reply]

Yes, it doesn't seem all that complicated, once we know exactly what each gene does, to figure out which combo will do what. This doesn't even really require a computer. The tricky part is figuring out exactly what each gene does in the first place. Then actually changing the genes isn't that easy either, requiring "programming" a virus to inject it. Having them remove existing genes is trickier still.

Where computers do seem to be critical is reading DNA. The most productive approach seems to be to read many small, overlapping fragments of DNA, then use computers to find the overlaps and piece it all together to find the entire genome of the individual. StuRat (talk) 16:47, 16 March 2015 (UTC)[reply]

Much Thanks! I suppose that it is possible to done the magnetization of biological cell so, that in the biological cell been done existence the computer’s software code, is it right?--83.237.194.120 (talk) 16:57, 16 March 2015 (UTC)[reply]

We have articles on this topic, including biocomputer and DNA computing. Looie496 (talk) 17:26, 16 March 2015 (UTC)[reply]

Thanks! I’m Looked’s through. So, meaning it is possible bit’s of DNA!--83.237.195.135 (talk) 18:02, 16 March 2015 (UTC)[reply]

What is a mutation from the point of vision of IT computer’s technologies (computer’s software)?--83.237.223.251 (talk) 19:25, 16 March 2015 (UTC)[reply]

Well, a disk error can cause a bit or series of bits to be reversed. Just like in biology, I would mostly expect this not to matter or to be bad, but occasionally (one in a million ?) you could get one that's actually helpful. However, since there is no mechanism to reproduce this single bit error, it wouldn't propagate. StuRat (talk) 23:20, 16 March 2015 (UTC)[reply]

Thank you! I assume that the mutation is always evolutionary jump (shift).--83.237.203.145 (talk) 05:43, 17 March 2015 (UTC)[reply]

Could evolution be in searching of the formerly losted (dismissed) evolutionary chain – bit’s?--83.237.203.145 (talk) 05:58, 17 March 2015 (UTC)[reply]

(Fairy funny joke - Could science exactly answer to the question whether been the first human on planet Earth a Cro-Magnon Teuton?)--83.237.197.10 (talk) 06:32, 17 March 2015 (UTC)[reply]

Did the computer is able to recover a losted source (initial) information complementing her by skipped (dismissed) logicality?--83.237.197.10 (talk) 07:31, 17 March 2015 (UTC)[reply]

Maybe evolution is always facing to backwards?--83.237.198.193 (talk) 09:11, 17 March 2015 (UTC)[reply]

Maybe the perfecting nature is constantly striving to recover the losted (dismissed) better perfect (sustainable) biological species?--83.237.218.251 (talk) 10:47, 17 March 2015 (UTC)[reply]

Your questions imply that you are under the impression that evolution has a goal and, possibly, some sort of plan. Evolution is a term used to describe a system in which things change over time. Commonly, when referring to animals, evolution is simply a term used to describe how a species changes over time to better fit the environment. The specific process is commonly referred to as "survival of the fittest." In the end, evolution isn't looking towards any goal. It is not intelligent and does not have a plan. It is merely a word used to state "things change." 209.149.114.176 (talk) 12:20, 17 March 2015 (UTC)[reply]

Thanks, for a fairy tale joke - The nature of Orthodoxes is always been consisted in the suppression of (struggle against to) the variability of biological species!--83.237.195.169 (talk) 13:23, 17 March 2015 (UTC)[reply]

Why is it believed dark-matter particles do not self-annihilate?

From e.g. Berlin et al. (2014) Simplified Dark Matter Models for the Galactic Center Gamma-Ray Excess, it seems to be the prevailing assumption that dark matter spontaneously decays into normal matter (quarks or leptons). I don't understand why this needs to be the case. Couldn't DM particles be their own antiparticles, and self-annihilate directly into gamma rays? — kwami (talk) 17:54, 16 March 2015 (UTC)[reply]

We don't know what we don't know about Dark matter, even if it exists. But when your fudge factor is 95% of your total, you start to wonder about the validity of your model. Rmhermen (talk) 18:56, 16 March 2015 (UTC)[reply]

(edit conflict) Then we would probably expect to see gamma rays, or similar high-energy electromagnetic radiation... and we don't! SLAC has some very nice archived public lectures on this topic: Deep Science: Mining for Dark Matter (2011) and The Dark Universe Through Einstein's Lens (2013) were both very interesting.

My take-away is that cold hydrogen gas provides a surprisingly consistent explanation for everything we observe about the "missing mass" problem, but a lot of observational astronomers (and a lot more of the popular science publications) are fixating on the exotic matter simply because it's more interesting. After all, what is the point of studying the parts of space that we already understand?

Nimur (talk) 18:58, 16 March 2015 (UTC)[reply]

We've been through this before. There is simply no way that hydrogen can explain dark matter, because its behavior is completely different. For one thing, the latest CMB data shows in section 3.3 that all baryonic matter in the universe make up only 4.8% of its energy density, compared to a dark matter density of 26%. Even your own link makes the point that dark matter cannot be made of atoms: "To account for the structure of galaxies and clusters of galaxies, the universe must contain six times more dark matter than ordinary atomic matter." Finally, the OP's paper is precisely about the "gamma rays, or similar high-energy electromagnetic radiation" that is consistent with dark matter self-annihilation in the galactic center. Its title is "Simplified Dark Matter Models for the Galactic Center Gamma-Ray Excess" (!!) --Bowlhover (talk) 19:48, 16 March 2015 (UTC)[reply]

That is the opposite of the prevailing assumption. From the abstract of the Berlin et al. paper:

"Taking a model-independent approach, we consider an exhaustive list of tree-level diagrams for dark matter annihilation, and determine which could account for the observed gamma-ray emission while simultaneously predicting a thermal relic abundance equal to the measured cosmological dark matter density."

"Dark matter annihilation" means self-annihilation. Self-annihilation does produce gamma rays, but it also produces other particle-antiparticle pairs, which the paper lists. --Bowlhover (talk) 19:13, 16 March 2015 (UTC)[reply]

Thank you! — kwami (talk) 20:35, 16 March 2015 (UTC)[reply]

Also note that in WIMP dark matter scenarios, self-annihilation is the usual mechanism that gets you to the right dark matter density in the early universe. The idea is that WIMPs were in equilibrium with photons above some temperature, and then "froze out" as the temperature decreased. They could still annihilate until the expansion of the universe made it unlikely for any two WIMPs to find each other. If the WIMPs have interactions on the scale of the weak force, this mechanism gives about the right density. --Amble (talk) 00:05, 17 March 2015 (UTC)[reply]

Electric clocks

I was reading a shopping catalogue which advised not plugging in an electric clock into an extension cable, especially if the extension is used to power a high load appliance, such as a heater, as it will cause the clock to gain time. Googling didn't lead me anywhere, except that electric clocks use the mains frequency to govern the timekeeping, and that high loads at the generating plant can lead to a reduction in the frequency - which would surely slow a clock, not make it run fast, and I can't believe one heater would affect the mains frequency. What am I missing? (edited)BbBrock (talk) 22:43, 16 March 2015 (UTC)[reply]

That advice seems wrong to me. I would expect a high local load to reduce the voltage available, not the frequency. StuRat (talk) 23:15, 16 March 2015 (UTC)[reply]

Wow, I think this may refer to (as stated above) the voltage, due to loading may drop-however slightly, but the mains frequency-increasing? I doubt it. Mains frequency is REALLY stable- I can't imagine that you plugging in your heater would affect it. there is a thing called power factor correction-referring to inductive/capacitive loads...mmm. which the heater is...*thinking* We need an electrician to answer this. Also, If the mains frequency changed-the utility company would be in REAL trouble!Read-write-services (talk) 23:34, 16 March 2015 (UTC)[reply]

Sounds dubious to me too. The speed of a synchronous motor (used in Synchrnous electric clocks), depends upon the frequency, and not the voltage, of the AC power supply; and this frequency is very carefully controlled (it is varied a bit for load sharing purposes between different power generators, but its average value is very stable). Abecedare (talk) 23:52, 16 March 2015 (UTC)[reply]

Are we asking about old-fashioned electric clocks, or modern electric clocks? Very few electric clocks in this century use synchronous motors that rely on frequency and display the time in analog fashion. Most modern (twenty-first century) electric clocks display the time in some digital fashion, usually with LEDs, and it is my understanding that most of them rely on a quartz crystal. A quartz crystal has an inherent resonant frequency and so should be extremely accurate anywhere in its proper operating range. I may be mistaken, having not done extensive research on the subject, but it isn't obvious to me what change in either voltage or frequency would change the resonance of a quartz crystal. Robert McClenon (talk) 01:53, 17 March 2015 (UTC)[reply]

See quartz clock for a discussion of the accuracy of quartz clocks. That article does not refer to any sensitivity to the voltage or frequency, but does note that nearly all modern electric clocks do use the quartz crystal technology. I think that the concern about dependency of the clock on the electrical input is exaggerated. Robert McClenon (talk) 01:58, 17 March 2015 (UTC)[reply]

Well, when unplugged and running on batteries, they do indeed keep abysmal time. However, there should be no timing signal in the electricity coming from the battery at all, so it must use quartz crystals there, but that doesn't explain why they keep time so poorly when on batteries. StuRat (talk) 02:01, 17 March 2015 (UTC)[reply]

^{[citation needed]}. You sound very confident, but my impression is that the ubiquitous cheap plug-in alarm clocks in the US are still primarily synchronous clocks tuned to mains frequency. As, I believe, are the clocks in most of the appliances where the clock is only a minor feature, like in a microwave, stove, coffeemaker, or DVD player. Such clocks are nonetheless pure digital, but there is no big electronic difference between tuning to a quartz oscillator and tuning to the mains oscillation, and using no quartz element saves money. Dragons flight (talk) 02:10, 17 March 2015 (UTC)[reply]

Such clocks will tend to exist within a DC circuit, and so their use of the AC oscillations sounds dubious and v.more expensive than using a quartz oscillator. Colour me unpersuaded. --Tagishsimon (talk) 02:49, 17 March 2015 (UTC)[reply]

Without saying exactly how common such clocks are, here is a news story discussing concerns about US clock instability tied to fluctuating mains frequency [2]. Here is a spec sheet for a digital alarm clock IC that uses mains frequency to keep time [3]. In that case, you have to tell the IC whether it is plugged into 50 Hz source or 60 Hz source. Dragons flight (talk) 03:07, 17 March 2015 (UTC)[reply]

WP:OR: I used to spend a lot of time listening to mains hum. In fact, my user page has a photograph of me on a government grant to listen for it. The power spectrum of commerically-delivered AC electricity is surprisingly broad-band. Look at the frequency spectrum in our article on mains hum. Look at this "Low Frequency Sounds" presentation which includes real measurements and includes the concise but very applicable statement, "Amplitude, phase, and instantaneous frequency are highly variable." Anybody who sets their clock by the power line - on the mistaken belief that the power line 60Hz frequency is very stable or very accurate - has not been measuring the frequency-stability of their clocks or their power-lines. The frequency of the power varies because the power station dynamo is non-ideal; and the aggregate electrical load is non-ideal; and the transmission line is non-ideal. This problem gets worse with complex interconnected electrical grids. Even if the power station had elaborate control systems to ensure that their AC power came out at 60.0000000 Hz, dispersion from the imperfect transmission would cause that signal to broaden. Phase noise - which is mathematically equivalent to frequency instability - is a natural consequence of the constantly-varying load as consumers of electric power increase and decrease their usage.

You can measure this yourself: you can build a home-brew VLF receiver using widely available hobbyist parts and you can hook it up to a computer's audio card and you can analyze the frequency spectrum of the electric power delivered to your own house. If you see a perfect spectral peak and no harmonics, your home receives 60.00000000 Hz with perfect frequency stability. If you live on Earth, that is not what you will measure. Nimur (talk) 03:46, 17 March 2015 (UTC)[reply]

Not sure how relevant the mains hum phenomenon is, since the power spectrum of the induced sound is not the same as the power spectrum of the electric signal. Since you have research experience in the area, do you have any plot the latter handy. I'd be interested in knowing what the main-lobe width is (the harmonics are of course irrelevant to the accuracy of a properly designed electric clock). Abecedare (talk) 04:08, 17 March 2015 (UTC)[reply]

To be more clear: the "hum" is a radio emission, and directly corresponds to the power spectrum of the, um, power. It is called hum because that's exactly what it sounds like if you connect a radio receiver to a speaker. (If you play in a rock band and your guitar doesn't have a humbucker, your guitar is a radio receiver ... and so are the wire leads that go into your amplifier, and so you may also hear that humming called "power line hum"). In supplement to this RF hum, you might also actually hear acoustic hum from a high-power electrical line; that can be caused by many factors, including thermal expansion and electroacoustic coupling. This direct conversion of electric power to acoustic energy is a lot messier, because it's almost definitionally caused by a nonlinear effect.

There are loads of spectrograms from worldwide collections hosted on the Stanford Very Low Frequency Research website. Those are power spectrums of (mostly natural) radio phenomena, and power line hum is almost always visible... even when the site is in a very remote location. Nimur (talk) 04:18, 17 March 2015 (UTC)[reply]

(edit conflict) OK, found this real-time display of power-line frequencies at various locations in US. Simply eye-balling the numbers the instantaneous frequency seems to be vary about +/- 0.02Hz, which if sustained would result in an accumulated time error of about 30s in a day! However, according to this North American Energy Standards Board document utilities apply a frequency correction once these clock timing errors exceed ~10 seconds, so that such errors don't continually add up (Aside: Ironically, such frequency corrections, would broaden the main-lobe of the power spectrum of the electric signal, but yet result in reduced timing error!). Abecedare (talk) 04:27, 17 March 2015 (UTC)[reply]

Indeed. A cheap quartz oscillator in a digital watch might have a Q factor of 10⁷ which would be some million times more stable than the AC mains. If you're still interested in worldwide data, here's the new spectrogram archive. If you look for ELF broadband spectra, you'll see the 60Hz lines with enough resolution to gauge their bandwidth. Nimur (talk) 04:32, 17 March 2015 (UTC)[reply]

Yes, the active adjustments to control the long-term average are discussed some in utility frequency stability. Dragons flight (talk) 04:36, 17 March 2015 (UTC)[reply]

Without going into rigorous mathematical gymnastics, the key takeaway is that it doesn't matter if the frequency is stable "on average" when you're using it to drive a clock. That's mathematically equivalent to saying that the "dc" component of the ac frequency is perfect! We don't really care if it "averages out" to being correct! We care about its instantaneous accuracy and its maximal deviation - in other words, at any particular time during the day, is the clock correct? Precisely, how wide is the frequency spread? This is its q factor, or bandwidth. Nimur (talk) 04:45, 17 March 2015 (UTC)[reply]

Here's an example from the Netherlands [4] that shows that a clock tied to the mains frequency as measured at a home wall outlet making an error of -10 to +50 seconds compared to a true clock over 70 days of sampling. A similar test in the US [5], where the average frequency is more tightly regulated, found an error of -5 to +10 seconds over 45 days. Either tolerance is presumably fine for most home application where you don't care about a high level of precision. Dragons flight (talk) 05:11, 17 March 2015 (UTC)[reply]

And for completeness (although I realize we have drifted - ha!- away from the original query): Here is a fun paper measuring the accuracy of 4 (inexpensive) quartz watches, to be 0.07 to 0.6 seconds a day (ie, since its drift is bounded, a mains-clock in US can be expected to be more accurate than a quartz watch after running 0.5-5 months). Btw, the measurement methods/watch analyzer sections of the paper reminded me of the torque calibration scene from My Cousin Vinny. :-) Abecedare (talk) 05:31, 17 March 2015 (UTC)[reply]

Many thanks to everyone who took the time to research and answer my question. I was skeptical of the claim, and I haven't read anything to make me change my mind on that. Thanks again everyone BbBrock (talk) 12:44, 17 March 2015 (UTC)[reply]

Ahah. Don't drop this so quick. This calls for you to email this shopping catalogue (pro bono) for a fuller explanation. You can point out that as Wikipedia Ref Desk drew a blank, then they may have miscarried and confused the manufacturers advice. Thus, misinforming their shoppers. The may have a technical enquires department (PR departs understand nothing -don't waste your time with them). Email them with the WP link - >https://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#Electric_clocks< and ask... “explain!” They will no doubt pride themselves, on giving good information to their customers, so they should have no problem with sorting out what the manufacture meant. The manufacturer may be in a place where English is not their first language and so tech things can easily get garbled. The shopping catalogue will ( I hope) realize, that as consumers we have a right to know and any delay in replying will look bad on them .Post those replies, back here, on a new section please.--Aspro (talk) 20:37, 17 March 2015 (UTC)[reply]

Aspro, I think I will do just that. This wasn't in some cheap tat catalogue, but one for a national health charity which specialises in environmental equipment for their clientele, and does pride itself on its good advice. Whilst this "pro tip" obviously won't negatively impact on anyone's health, I'm sure they won't want unsubstantiated information in their catalogue. I'll let you know BbBrock (talk) 22:12, 17 March 2015 (UTC)[reply]

I still don't understand why anyone at all uses a clock with a cord. They are inaccurate, constantly prone to power outages that means they are unreliable, consume absurd amounts of energy, and are no cheaper than LCD clocks that can run well over five years on a single AA battery, which are capable of quite a loud alarm. The bizarre part is that it is harder to find the good clocks than the insane ones at the market, a pathology of commerce I cannot understand. Wnt (talk) 03:28, 18 March 2015 (UTC)[reply]

It may be a clock for people that suffer from seasonal affective disorder in which case it may well have a 20 watt incandescent bulb. An AA battery is just not a solution for all clock applications.--Aspro (talk) 17:19, 18 March 2015 (UTC)[reply]