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{{Misplaced Pages:Reference_desk/Archives/Science/2013 October 27}} | |||
{{Misplaced Pages:Reference_desk/Archives/Science/2013 October 28}} | |||
= October 29 = | |||
= December 13 = | |||
== What is the most iconic tornado photo == | |||
] | |||
{{hat|Request for opinions}} | |||
What photo of a tornado would you say is the most iconic? I'm researching the history of tornado photography for an eventual article on it and I've seen several specific tornadoes pop up over and over again, particularly the ] and the "dead man walking" shot of the ]. Which would be considered more iconic? ] | ] | ] 17:21, 13 December 2024 (UTC) | |||
:At the top of this page is a bullet point stating "We don't answer requests for opinions, predictions or debate": this reads to me like a request for subjective opinions. Perhaps you would like to consider what quantifiable and referenceable metric would answer what you want to know? | |||
I'm trying to use a simple voltage divider to allow me to measure a variable resistance that ranges from around 10k ohm down to nearly zero using an ] microcontroller (like in an ]). The circuit is the one shown at right (from our ] article - which I've read). | |||
:Presumably you also want only real tornadoes considered? Otherwise some might nominate the the twister from ], or from more recent tornado-related movies – ], anyone? :-). {The poster formerly known as 87.81.230.195} ] (]) 18:07, 13 December 2024 (UTC) | |||
:"Swegle Studios" has a couple of YouTube videos dedicated to the backstories of famous tornado photos and video; you might find them useful in your research. , . ] (]) 18:40, 13 December 2024 (UTC) | |||
:I googled "most iconic tornado photo" and a bunch of different possibilities popped up. I don't see how you could say that any given photo is the "most iconic". ←] <sup>'']''</sup> ]→ 18:57, 13 December 2024 (UTC) | |||
Vin is 5 volts and the analog-to-digital converter is connected to Vout and measures 0 to 5 volts with a precision of one part in 1024. I'm trying to figure out whether I should make R<sub>1</sub> or R<sub>2</sub> be the variable resistor - and what value to use for the other (fixed) resistor. From the math: | |||
{{hab}} | |||
: V<sub>out</sub>/V<sub>in</sub> = R<sub>2</sub> / (R<sub>1</sub> + R<sub>2</sub>) | |||
= December 15 = | |||
Which suggests that if R<sub>1</sub> is the variable resistor, then R<sub>2</sub> should be very small in order to use the entire range of the AtoD converter. (For example, if R<sub>2</sub> is 10k ohms - then all of my results will be in the range 2.5v to 5.0v and I'll be wasting one whole bit of the result...but if it's just 10 ohms, then I'd be using almost the entire range of the AtoD. I'm betting that something will go horribly wrong if I make R<sub>2</sub> be as small as 10 ohms. What's the gotcha and what's the recommended value? | |||
== help to identify ] == | |||
(I'm not really interested in investigating more complicated circuits - I'm engineering down to a price here!). | |||
] in New South Wales Australia]] Did I get species right? Thanks. ] (], ]) 06:56, 15 December 2024 (UTC) | |||
] (]) 02:57, 29 October 2013 (UTC) | |||
:related: https://species.wikimedia.org/Wikispecies:Village_Pump#help_to_identify_species ] (], ]) 06:57, 15 December 2024 (UTC) | |||
:Wouldn't it be simpler to use a three terminal variable resistor, with one end of the resistor connected to +5 V, the other end to ground, and the wiper connected to the A/D converter? This would assure a low (0.5 mA) current through the resistor and a negligible current through the wiper. ] (]) 03:14, 29 October 2013 (UTC) | |||
:FWIW, I can't detect any visible differences between the plant in this photo and the ones illustrated in the ] and the ] articles. However, the latter makes it clear that ''Polygala'' is a large genus, and is cultivated, with hybrids, so it's possible that this one could be a close relative that differs in ways not visible here, such as in the bark or roots. That may or may not matter for your purposes. {The poster formerly known as 87.81.230.195} ] (]) 10:11, 15 December 2024 (UTC) | |||
::If I was using a potentiometer - yes. That would be nice because R<sub>1</sub>+R<sub>2</sub> is a constant and V<sub>out</sub> is directly proportional to R<sub>2</sub> - but I'm not. There is just one external variable resistance that I'm measuring and R<sub>2</sub> is fixed. (Although if there was a good reason to do it, I could make R<sub>2</sub> be the variable one and R<sub>1</sub> be the fixed resistance. ] (]) 03:39, 29 October 2013 (UTC) | |||
== How to address changes to taxonomy == | |||
:::On the "betting that something will go horribly wrong", you need to watch the potential power dissipation in each of the resistors, e.g. 0.5 A and 2.5 W with your value of 10 ohm. That's a pretty hefty resistor, and may cost a few cents more. If your variable resistor can dissipate less power than the fixed resistor, it may overheat when it is at a similar value. Another gotcha is that over most of the range of the variable resistor (> 10 ohm), your resolution is going to be far worse than if you use a larger fixed resistor. You should plot the resolution over the whole range, and how it is spread over the range compared to where you want it. For example, you may want substantially more resolution at lowish values of resistance at the expense of at the high resistance end, in which case you could use a lowish value (e.g. 1 kiloohm, 90% of your ADC range, quite nonlinear; 10 kiloohm: substantially more linear, 50% of the ADC range). In your diagram, which resistor is which makes no real difference: the results are simply reversed, non-linearities and all (subtract from 1023). — ] 03:48, 29 October 2013 (UTC) | |||
Hi all, | |||
:Another, slightly more complicated way of doing it (I know you said you're not interested, but it's still cheap) is to convert the resistance into a delay and measure that. ] gives a good example of how the dirt-cheap and ubiquitous 555 timer (or similar methods) were used to measure the position of joysticks, which produced a variable resistance and had to be read with a digital device. Basically, you charge a capacitor and the resistance determines how long it takes to charge it. You can time that and know what the resistance is. The accuracy isn't great, but it is simple to set up in a way that doesn't damage components with too much current, which can be a serious problem for reading the whole range with a voltage divider. ] (]) 11:47, 29 October 2013 (UTC) | |||
I am a biology student brand new to wiki editing who is interested in cleaning up small articles/stubs for less known taxa. One that I've encountered is a mushroom that occurs in the pacific northwest ('']''). The article mentions that this fungus is occasionally mistaken for another fungus, '']''. <br> | |||
::The key thing the 555 brings to the table here is the ability to send a trigger pulse then wait for a response using all digital I/O. Since you have an analog input, you could just watch the voltage of the capacitor directly as it charges from a digital output if you want to avoid the chip. ] (]) 11:49, 29 October 2013 (UTC) | |||
However, the issue I've run into is that ''F. pinicola'' used to be considered a single species found around the world, but relatively recently was split into a few different species. The original name was given to the one that occurs in Europe, and the one in the pacific northwest (and thus could be mistaken for ''F. ochracea'') was given the name '']''. | |||
:An important piece missing is tolerance and accuracy. If your fixed resistor is 5% but 10k, you can forget being accurate at the low end. You would already be bit limited 10 ohms/bit, but also +/- 500 ohms (50 bits) for resistor tolerance. Without knowing your tolerance for error and where you need accuracy, it's not very tractable. Other alternatives are to use a equal voltage divider to supply the reference voltage to the A/D (zero it out) and then have the same circuit with the DUT in parallel to R2. The more you can ratio out error, the better your accuracy. With just the voltage divider, resistor tolerance, temperature and device selection will all impact your measurement and at the low end, it will be useless. You always want to be close to full scale.--] (]) 12:52, 29 October 2013 (UTC) | |||
<br> | |||
The wiki page says <blockquote><p>Historically, this fungus has been misidentified as ''F. pinicola.'' When both species are immature, they can look very similar, but can be distinguished by lighting a match next to the surface of the fungus. ''F. pinicola'' will boil and melt in heat, while F. ochracea will not.</p></blockquote> | |||
<br>Since the source says ''pinicola'' (as likely do most/all other sources of this info given the change was so recent), and since technically it's true that they used to be mistaken for it... what would be the most appropriate way to modernize that section? | |||
<br> | |||
<B>My questions are</b>: | |||
:You know more about this than I do, but my thought is that whatever you're using this for, wasting power is always bad, so you want as high a value as possible for R1 so that no matter what goes wrong with the rest of the circuit, you know your power isn't peeing away through it. You then want your other variable resistor to also be as high as possible so that you can get nearly the full range by turning it up higher than R1. Which gets us to the brass tacks: what is the resistance of your voltmeter '''really'''? A hypothetical voltmeter passes zero current, so you could use a chunk of wood for R1 and R2 and move the probe needle back and forth on it. Unfortunately this is not a purely hypothetical voltmeter, so you need R1 << maximum R2 << Rvoltmeter. ] (]) 16:35, 29 October 2013 (UTC) | |||
Should I replace ''F. pinicola'' with ''F. mounceae''? Or is that wrong because the source doesn't refer to it by that name? Would it be better to write something like (now known as/considered ''F. mounceae'') next to the first mention of the species? Or is that a poor choice because it implies all the members of ''F. pinicola'' were renamed ''F. mounceae''? | |||
<br /> | |||
<br> | |||
:If you want to use a simple voltage divider, I would choose two fixed resistors, with R<sub>1</sub>+R<sub>var</sub> in place of R<sub>1</sub>, R<sub>var</sub> being the variable resistor now. V<sub>out</sub>/V<sub>in</sub> = R<sub>2</sub> / (R<sub>1</sub> + R<sub>var</sub> + R<sub>2</sub>). With R<sub>1</sub>= 100 R<sub>2</sub> = 1000, R<sub>var</sub> between 0 and 10k, Vout will be between 0.45 and 4.55V (assuming 5V input). Absolute precision goes down when the variable resistance rises, but the relative precision will be highest when R<sub>var</sub> equals R<sub>1</sub>+R<sub>2</sub>. Example: Voltage difference between R<sub>var</sub> = 100 and = 110 is 0.0344V, between 2000 and 2200 it's 0.098V, between 8000 and 8800 it's 0.044V. ] (]) 08:36, 30 October 2013 (UTC) | |||
::Replace R2 with alow value capacitor, make Vin come from an output of the u controller and use software (free) to. work out the restance:)--] (]) 22:28, 30 October 2013 (UTC) | |||
Any advice on how to go about updating this section is incredibly appreciated | |||
== Questions about Dietry Fibers == | |||
<br> | |||
] (]) 10:21, 15 December 2024 (UTC) | |||
:::First, take these sorts of questions to the relevant Wikiproject, in this case ]. I am not as familiar with the consensus at ], but it seems like they defer to '']'' and ] to decide. Those sources presently seem to consider '']'' a good species. Also, be careful about "replacing", there are rules to ensure the continuity of the article history. By the way, there is a hilarious but unencyclopedic/copyvio recipe appended to the '']'' article. <span style="font-family: Cambria;"> ] (])</span> 11:09, 15 December 2024 (UTC) | |||
::::Thanks for the tips, I didn't know about projects so I'll go read up on that. And thanks for the warnings about replacing things. I've been reading a lot of help pages, but I'm still in the process of learning the all conventions and what mechanics break if you do things the wrong way. | |||
::::I actually saw the recipe ages ago before I made my account and completely forgot about it... it was one of many things that prompted me to get into wiki editing. ] (]) 23:12, 15 December 2024 (UTC) | |||
== Does stopping masturbation lead to sperm DNA damage? == | |||
1) Why fibers are not considered ]s? | |||
I'm looking for information on the potential link between the frequency of ejaculation (specifically through masturbation) and sperm DNA damage. I've come across some conflicting information and would appreciate it if someone could point me towards reliable scientific studies or reviews that address this topic. | |||
2) What is the main source of the most coveted source for insoluble fiber by humans? | |||
Specifically, I'm interested in whether prolonged periods of abstinence from ejaculation might have any negative effects on sperm DNA integrity. Any insights or links to relevant research would be greatly appreciated. ] (]) 17:08, 15 December 2024 (UTC) | |||
3) Is there such a concept "correct ratio between soluble and insoluble fiber in a human's diet?" | |||
:Only males may abstain from sperm-releasing ] that serves to flush the genital tract of old sperm that in any case will eventually dissipate. No causal relationship between masturbation and any form of mental or physical disorder has been found but abstinence may be thought or taught]]] to increase the chance of wanted conception during subsequent intercourse. ] (]) 00:51, 16 December 2024 (UTC) | |||
::There's many rumors about that topic. One is that not ejaculating frequently increases the risk of developing ]. <span style="font-family: Cambria;"> ] (])</span> 01:02, 16 December 2024 (UTC) | |||
:Nothing really conclusive but there's some evidence that short periods are associated with lower DNA fragmentation, see<small> | |||
:* {{Cite journal |last=Du |first=Chengchao |last2=Li |first2=Yi |last3=Yin |first3=Chongyang |last4=Luo |first4=Xuefeng |last5=Pan |first5=Xiangcheng |date=10 January 2024 |title=Association of abstinence time with semen quality and fertility outcomes: a systematic review and dose–response meta‐analysis |url=https://onlinelibrary.wiley.com/doi/10.1111/andr.13583 |journal=Andrology |language=en |volume=12 |issue=6 |pages=1224–1235 |doi=10.1111/andr.13583 |issn=2047-2919}} | |||
:* {{Cite journal |last=Hanson |first=Brent M. |last2=Aston |first2=Kenneth I. |last3=Jenkins |first3=Tim G. |last4=Carrell |first4=Douglas T. |last5=Hotaling |first5=James M. |date=16 November 2017 |title=The impact of ejaculatory abstinence on semen analysis parameters: a systematic review |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC5845044/ |journal=Journal of Assisted Reproduction and Genetics |language=en |volume=35 |issue=2 |pages=213 |doi=10.1007/s10815-017-1086-0 |issn=2047-2919 |pmc=5845044 |pmid=29143943}} | |||
:* {{Cite journal |last=Ayad |first=Bashir M. |last2=Horst |first2=Gerhard Van der |last3=Plessis |first3=Stefan S. Du |last4=Carrell |first4=Douglas T. |last5=Hotaling |first5=James M. |date=14 October 2017 |title=Revisiting The Relationship between The Ejaculatory Abstinence Period and Semen Characteristics |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC5641453/ |journal=International Journal of Fertility & Sterility |language=en |volume=11 |issue=4 |pages=238 |doi=10.22074/ijfs.2018.5192 |issn=2047-2919 |pmc=5641453 |pmid=29043697}} | |||
:</small> | |||
:for example. ] (] • ]) 02:12, 16 December 2024 (UTC) | |||
:Mature sperm cells do not have ] capability.<sup></sup> Inevitably, as sperm cells get older, they will naturally and unavoidably be subject to more and more ]. Obviously, freshly produced spermatozoa will, on average, have less DNA damage. It is reasonable to assume that the expected amount of damage is proportional to the age of the cells, which is consistent with what studies appear to find. Also, obviously, the more the damage is to a spermatozoon fertilizing an oocyte, the larger the likelihood that the ] in the resulting zygote, which does have DNA repair capability, will be incomplete. The studies I've looked at did not allow me to assess how much this is of practical significance. --] 09:40, 16 December 2024 (UTC) | |||
= December 16 = | |||
Thanks very much for an answer. ] (]) 05:48, 29 October 2013 (UTC) | |||
== ] == | |||
:I numbered your Q's for easier response: | |||
Thanks to those who answered my ], I think it should be added to a disambiguation page. If anyone wants to help me write that, reach out. | |||
:1) A nutrient is something you digest. Since fiber is not digested, it's not a nutrient. At least that's true of ]. ] (]) 21:59, 29 October 2013 (UTC) | |||
A sandpile seems disorganized and inert, but these are critically self-organizing. Do the frequency and size of disturbances on sand dunes and snowy peaks follow power law distribution? | |||
== Wouldn't retrograde amnesia erase a person's mental illnesses too? == | |||
] (]) 01:18, 16 December 2024 (UTC) | |||
:Shouldn't this be at the Math Desk? <span style="font-family: Cambria;"> ] (])</span> 05:12, 16 December 2024 (UTC) | |||
::If the question is not about the model mentioned in the heading but about the physical properties of sand dunes and snowy peaks, this here is the right section of the Reference desk. --] 08:51, 16 December 2024 (UTC) | |||
:::I await a non-mathematical answer. <span style="font-family: Cambria;"> ] (])</span> 09:23, 16 December 2024 (UTC) | |||
::::It depends is probably a fairly reasonable non-mathematical answer for these kinds of systems. For sand dunes anyway, sometimes avalanche frequency is irregular and the size distribution follows a power law, and sometimes it's close to periodic and the avalanches span the whole system. It seems there are multiple regimes, and these kinds of systems switch between them. ] (]) 09:35, 16 December 2024 (UTC) | |||
:::::Thank you! I'm impressed this seems so casual, but surely you read this somewhere that might have a URL? | |||
:::::] (]) 22:29, 19 December 2024 (UTC) | |||
:Hi, this is an interesting and somewhat open question! A lot of work is done on these models but much less on careful analyses of real dunes. I did find that is freely accessible and describes some physical experiments and how well they fit various models. The general answer seems to be that the power law models are highly idealized, and determining the degree to which any real system's behavior is predicted by the model ahead of time is very difficult. Update: and it does include discussion of how well the model fits experiments.] (]) 17:21, 16 December 2024 (UTC) | |||
If an adult with several mental illnesses or emotional problems and specific fears had an accident and woke up in the hospital with no memories at all like that was their first second being alive, wouldn't their mental illnesses, emotional problems and specific fears be gone too? <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 07:03, 29 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
::That dissertation is great! | |||
:No. There are multiple problems with that idea, one of which is that mental illnesses aren't purely based on what's in a person's episodic and declarative memory. See ]. ] (]) 07:57, 29 October 2013 (UTC) | |||
::] (]) 22:30, 19 December 2024 (UTC) | |||
:Life is not like a video game. We can't reset back to an earlier time. Mental disease will no more disappear just because of forgetting than grey hair will turn black. ] (]) 11:08, 29 October 2013 (UTC) | |||
::What would or could be forgotten is whatever was experienced previously. Also, is the hypothetical person able to speak and do other things normally? ←] <sup>'']''</sup> ]→ 11:17, 29 October 2013 (UTC) | |||
:::It depends on the extent of the damage that caused the amnesia. Different areas of the brain cover different functions, so damage to one (for example, to the ability to recall memories) would not necessarily cause problems for other areas of the brain (for example, language processing or physical coordination). --]''''']''''' 12:15, 29 October 2013 (UTC) | |||
== Polar night == | |||
*The answer is a bit complicated, and involves several factors. | |||
#It is common in movies and TV shows for somebody to wake up with no memory whatsoever, but that almost never happens in real life. Genuine retrograde amnesia eliminates memory for the recent past -- sometimes extending back for years -- but almost always leaves memory from childhood intact. There are a few exceptions, but most of them have dubious features -- in some cases it is not clear whether people are faking TV-style amnesia in order to avoid answering awkward questions. | |||
#The idea that all, or most, mental illness results from traumatic experience is a relic of Freudian theory that is now rejected by the great majority of psychiatrists. | |||
Are there any common or scientific names for types of polar night? The types that I use are: | |||
:So the bottom line is that (a) that doesn't happen, and (b) it wouldn't eliminate most types of mental illness even if it did. ] (]) 16:59, 29 October 2013 (UTC) | |||
* ''polar night'' - meaning a day when sun's altitude remains below horizon entire day (there is no daylight at solar noon, only civil twilight), occurring poleward from 67°24′ north or south | |||
* ''civil polar night'' - meaning a day when sun's altitude remains below -6° entire day (there is no civil twilight at solar noon, only nautical twilight), occurring poleward from 72°34′ north or south | |||
* ''nautical polar night'' - meaning a day when sun's altitude remains below -12° entire day (there is no nautical twilight at solar noon, only astronomical twilight), occurring poleward from 78°34′ north or south | |||
* ''astronomical polar night'' - meaning a day when sun's altitude remains below -18° entire day (there is no astronomical twilight at solar noon, only night), occurring poleward from 84°34′ north or south | |||
These names were changed on ] article, and I wnat to know whether these named I listed are in use in any scientific papers, or in common language. (And I posted that question here and not in language desk because I think that this is not related to language very tightly.) | |||
Meck, Su has this kind of retrograde amnesia and though it is rare she isn't the only person to have a complete loss of all memories. Baseball_Bugs, in this case the person would be like an infant and would have to be taught everything again. <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 02:30, 30 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
--] (]) 18:56, 16 December 2024 (UTC) | |||
: |
:Some definitions at from the ]. ] (]) 22:55, 16 December 2024 (UTC) | ||
::These seem to be generalizable as: X polar night is a period, lasting not less than 24 hours, during which the sun remains below the horizon and there is no X twilight. The specific definitions depend then on the specific definitions of ]/]/]. These can be defined with a subjective observational standard or with an (originally experimentally determined) objective standard. --] 10:36, 17 December 2024 (UTC) | |||
:::FWIW, I as a former amateur astronomer have never previously thought about the question of ''Polar'' twilight and night nomenclatures, but immediately and completely understood what the (previously unencountered) terms used in the query must mean without having to read the attached descriptions. {The poster formerly known as 87.81.230.195} ] (]) 16:34, 17 December 2024 (UTC) | |||
= December 17 = | |||
::<small>I'm sure Kirk volunteered to show her where she sleeps at night. ] (]) 02:40, 30 October 2013 (UTC) </small> | |||
== differential equations with complex coefficients == | |||
:I looked up the Su Meck case, and while it's mostly popular-press stuff, it is very much an impressive story. --] (]) 02:53, 30 October 2013 (UTC) | |||
In an intro ODE class one basically studies the equation <math>\dot x=Ax</math> where x is a real vector and A is a real matrix. A typically has complex eigenvalues, giving a periodic or oscillating solution to the equation. That is very important in physics, which has various sorts of harmonic oscillators everywhere. If A and x are complex instead of real, mathematically the ODE theory works out about the same way. I don't know what happens with PDE's since I haven't really studied them. | |||
Even in cases where mental illness might be caused (or triggered) by trauma, erasing the memories of the traumatic experiences would not erase the mental effects of the traumatic experiences. My cat doesn't have to specifically remember being sprayed with water to react to the sight of a spray bottle. ] (]) 18:07, 31 October 2013 (UTC) | |||
My question is whether the complex case is important in physics the way the real case is. Can one arrive at it through straightforward coordinate transformations? Do the complex eigenvalues "output" from one equation find their way into the "input" of some other equation? Does the distance metric matter? I.e. in math and old-fashioned physics we use the Euclidean metric, but in realtivity one uses the Minkowski metric, so I'm wondering if that leads to complex numbers. This is all motivated partly by wondering where all the complex numbers in quantum mechanics come from. Thanks. ] (]) 22:54, 17 December 2024 (UTC) | |||
== Side-stick controls in cockpits == | |||
:Perhaps I don't understand what you are getting at but simple harmonic motion is xdot=j*w*x where w is angular frequency and j is i ] (]) 00:35, 18 December 2024 (UTC) | |||
This is just a quick question: when Airbus designed the ], the first fly-by-wire airliner, what were the reasons why they decided to use side-stick controls (which, at the time, was probably unheard of for commercial aircraft) instead of the conventional yokes, and what were the reasons why Boeing decided not to use side-stick controls in the ] and ]? Also, what are the advantages and disadvantages of using side-stick controls in commercial aircraft cockpits? I have read our Misplaced Pages articles for yokes and side-sticks, but they do not elaborate on the information I want answered here. ] <sup>]]]]</sup> 10:39, 29 October 2013 (UTC) | |||
:If PDEs count, the ] and the ] are examples of differential equations in the complex domain. A linear differential equation of the form <math>\dot x=Ax</math> on the complex vector space <math>\mathbb{C}^n</math> can be turned into one on the real vector space <math>\mathbb{R}^{2n}</math>. For a very simple example, using <math>n=1,</math> the equation <math>\begin{bmatrix}\dot z\end{bmatrix} = \begin{bmatrix}i\end{bmatrix}\begin{bmatrix}z\end{bmatrix}</math> can be replaced by | |||
:As a pilot that flies small planes, the ] vs ] (and both are mechanical, not fly-by-wire), the sidestick is out of the way of the display and doesn't feel all that different from the left seat (captains seat) than a traditional center yoke. There is also the feeling of more room. The downside is that the left/right seat switches are reversed (some would be anyway for throttle control while PTT). An obvious advantage of the center yoke is either hand can fly and either pilot can see and reach the other yoke. The requirements for the quick donning mask, for instance, might be easier to accomplish with this feature. Even the fly-by-wire yokes have mechanical feedbacks to mimic what would be felt in a traditional mechanical yoke so the transition is easier like the buffet before a stall is mimicked (I'm not sure about side-stick though). Personally, I like the Cirrus side stick just for the added space. Side stick fighter planes normally have the stick on the right with throttle control either on the stick or left side so opposite the captain's seat. In the end though, it comes down to transition time. If everything looks and works the same and the only difference is fly-by-wire vs hydraulic, a transition will be much easier. If there a number of differences, like how/when the autothrottle engages/disengages or where switches are located (stick or console), transition time can be longer, more expensive and possibly less safe. I suspect the yoke and controls on the yoke, the travel distance for rotation, bank angle for standard rate turn, etc, all match previous Boeing airplanes and makes transitioning easier and quicker (cheaper). The crash in San Francisco recently was attributed initially to a small difference in autothrottle behavior between types. Small things that change can have large consequences even if the change appears good on paper. --] (]) 12:04, 29 October 2013 (UTC) | |||
::<math>\begin{bmatrix}\dot x\\\dot y\end{bmatrix} = \begin{bmatrix}0&-1\\1&0\end{bmatrix}\begin{bmatrix}x\\y\end{bmatrix}.</math> | |||
::In jet airliners like Airbus and Boeing, the pilots actually spend a very small percentage of the flight with hands on the control - most of the time the aircraft is being flown by the autopilot. Pilots spend a much greater percentage of their time monitoring instruments, monitoring information displays and doing things with documents - hence the attraction of the Airbus strategy of providing a stick at the side of the pilot and a tray table directly in front. All flight controls are fully powered by servo motors so a large stick with a large moment arm is not necessary. And why has Boeing stayed with the conventional control yoke? Probably because Boeing is the market leader so it doesn't need to try new strategies as Airbus does in an attempt to establish its product and then increase market share. Also, Boeing places great importance on what its established customers say and want in their future aircraft. It seems likely to me that when Boeing asks its established customers and their pilots, all say they are entirely happy with what they have at present. ] ''(])'' 12:23, 29 October 2013 (UTC) | |||
: --] 01:11, 18 December 2024 (UTC) | |||
:::Shouldn't this be at the Math Desk? It almost seems like the IP could be trolling, given the same question just above. <span style="font-family: Cambria;"> ] (])</span> 14:49, 18 December 2024 (UTC) | |||
::::The question whether the complex case is important <u>in physics</u> the way the real case is, is not a maths issue. IMO the Science section is the best choice. I do not see another post that asks the same or even a related question. --] 21:51, 18 December 2024 (UTC) | |||
:::::Just as above, I await a non-mathematical answer to this question. <span style="font-family: Cambria;"> ] (])</span> 07:01, 19 December 2024 (UTC) | |||
Thanks all. Greglocock, your SHO example is 1-dimensional but of course you can have a periodic oscillator (such as a planetary orbit) in any orientation in space, you can have damped or forced harmonic oscillators, etc. Those are all described by the same matrix equation. The periodic case means that the matrix eigenvalues are purely imaginary. The damped and forced cases are where there is a real part that is negative or positive respectively. Abductive, of course plenty of science questions (say about how to calculate an electron's trajectory using Maxwell's equations) will have mathematical answers, and the science desk is clearly still the right place for them, as they are things you would study in science class rather than math class. Lambiam, thanks, yes, PDE's are fine, and of course quantum mechanics uses complex PDE's. What I was hoping to see was a situation where you start out with real-valued DEs in some complicated system, and then through some coupling or something, you end up with complex-valued DEs due to real matrices having complex eigenvalues. Also I think the Minkowski metric can be treated like the Euclidean one where the time coordinate is imaginary. But I don't know how this really works, and Misplaced Pages's articles about such topics always make me first want to go learn more math (Lie algebras in this case). Maybe someday. ] (]) 07:25, 19 December 2024 (UTC) | |||
:It is worth noting that the most important differences between the Boeing and Airbus fly-by-wire control really aren't in the shape and position of the yoke or side-stick, but rather in the way that the aircraft's computer interprets, responds to, and feeds back pressure on the yoke or stick. There is much information and discussion (correct and otherwise) available in online fora; see for instance . (You will find many online flamewars about ] philosophies of Boeing versus Airbus.) The Airbus system has a number of unambiguous benefits from a design and economics standpoint—it is lighter and mechanically simpler; it seems to be ergonomically preferable (less tiring for pilots, room for a tray in front of the pilot, no problems with controls obstructing the view of instruments); removing the yoke allows the cockpit to be slightly shallower from front to back. | |||
:The safety question is difficult to settle. What you will find fairly readily are a small number of edge-case incidents and crashes which each side's proponents like to cite over and over, saying "''in this tiny one-off case, our preferred technology could have/did save(d) the day''". ](]) 16:55, 30 October 2013 (UTC) | |||
= December 18 = | |||
== Animal learning by experiences of other animals without direct exposure themselves... == | |||
== Why don't all mast radiators have top hats? == | |||
It may sound like a confusing or misleading title, but what I am getting at is the instance of having an animal experience some sort of distress by a specific type of predator that looks a particular way. Instead of reacting by instinct, the animal that experiences the stress passes on the learning or conditioning by communication or language, no matter how rudimentary it is. That way, successive generations of the same species can learn who to avoid rather than relying on instinct all the time. In a similar story about lyre birds, if I remember correctly, young male lyre birds can learn the songs of older lyre birds and imitate them. I am wondering if there are any more specific cases in the animal kingdom, but are more sophisticated/complex than the ones I've described and are occurring in nonhuman species. I already know that humans can do it. So, please don't list ''homo sapiens'' or any member of the ''homo'' genus unless it is an exception. ] (]) 13:32, 29 October 2013 (UTC) | |||
]Our ] article describes a device called a "top hat" which increases the range for mast radiators that can't be built tall enough. | |||
:It has been shown shown that primates do not have an inborn fear of predators such as snakes but they learn this behaviour from other primates. However, although they can be conditioned in the lab to fear predators by showing them videos of other members of their species showing a fear response, the same process won't necessarily condition them to fear other objects. As it says "When videos were spliced so that identical displays of fear were modeled in response to toy snakes and flowers, or to toy crocodiles and rabbits( (M. Cook & Mineka, 1991), the lab-reared monkeys showed substantial conditioning to toy snakes and crocodiles, but not to flowers and toy rabbits". So they suggest that there is also an evolutionary component to the selective learning. <span style="text-shadow:grey 0.2em 0.2em 0.1em; class=texhtml">]</span> ] 14:23, 29 October 2013 (UTC) | |||
::Concidentally or otherwise, the information you're stating was covered in an NPR discussion just yesterday. :) Which means there could be a link to it on their website, if someone wants to hear more about it. ←] <sup>'']''</sup> ]→ 23:19, 29 October 2013 (UTC) | |||
:::Are you going to link the article? ] (]) 16:18, 30 October 2013 (UTC) | |||
:We have a moderately lengthy article on ], with some material about animals. A Google Scholar search for "observational learning animals" will give you a lot more material -- for example, rats learning which foods are good to eat by observing other rats. ] (]) 16:44, 29 October 2013 (UTC) | |||
So, why would you bother building a mast radiator without a top hat? Couldn't you just build it shorter with the top hat, and save steel? ] (]) 15:00, 18 December 2024 (UTC) | |||
::Might be the masks made them scarier. As suggests, humans are naturally freaked by not-quite-human faces, due to the expectation of a regular one. Crows have lived among us as long as we have, so it seems (to me) they could have the same issue. Might be why scarecrows exist. ] ] 06:04, ], ] (UTC) | |||
:The main source cited in our article states, "{{tq|Top loading is less desirable than increased tower height but is useful where towers must be electrically short due to either extremely low carrier frequencies or to aeronautical limitations. Top loading increases the base resistance and lowers the capacitive base reactance, thus reducing the ''Q'' and improving the bandwidth of towers less than 90° high.}}"<sup></sup> If "reducing the {{serif|''Q''}}" is an undesirable effect, this is a trade-off design issue in which height seems to be favoured if circumstances permit. --] 21:41, 18 December 2024 (UTC) | |||
:One of my psychology students had trained a rat to press a lever repeatedly to get a reward, and wanted to see if a "student rat" could learn to press the lever to get the reward just by watching the "teacher rat" do the act. The result was that Student rat just hung around by the water dipper to enjoy the reward which was earned by the Teacher rat. The Student did not learn that pressing the lever was what brought the reward. ] (]) 04:24, 30 October 2013 (UTC) | |||
== Name of our solar system == | |||
::<small>And did they call this Student Rat a StuRat, for short ? :-) ] (]) 17:07, 31 October 2013 (UTC) </small> | |||
Is our star system officially called "Sol", or is that just something that came from science fiction and then became ubiquitous? ] (]) 22:06, 18 December 2024 (UTC) | |||
== Does anybody know how many citations an article has been cited? == | |||
:It's called the ], and its star is called Sol, from Latin via French. Hence terms like "solstice", which means "sun stands still" in its apparent annual "sine wave" shaped path through the sky. ←] <sup>'']''</sup> ]→ 23:31, 18 December 2024 (UTC) | |||
:::Via French? According to the OED, it came direct from Latin.<sup></sup> --] 11:45, 19 December 2024 (UTC)}} | |||
::::Old French plus Latin. ←] <sup>'']''</sup> ]→ 14:25, 19 December 2024 (UTC) | |||
:::::Also in Old French, the word meaning "sun" was '']''. --] 23:42, 19 December 2024 (UTC) | |||
::Let's say {{fact}} to that claim. The star is indeed called Sol if you're speaking Latin, but in English it's the Sun (or sun). Of course words like "solar" and "solstice" derive from the Latin name, but using "Sol" to mean "the Sun" does seem to be something from science fiction. --] (]) 06:04, 19 December 2024 (UTC) | |||
:::"Sol" is occasionally used to mean the Sun by astronomers. I feel like it is used in contexts where it is necessary to distinguish our experience with the Sun here on Earth, such as sunsets, from more "sterile" aspects of the Sun one might experience off the Earth. <span style="font-family: Cambria;"> ] (])</span> 08:56, 19 December 2024 (UTC) | |||
::::Being an astronomer myself, I don't think I've ever heard anyone use "Sol" outside of a science fiction context. --] (]) 09:06, 19 December 2024 (UTC) | |||
::::::Scientific articles that use the term Sol; and . These are rather speculative but as I mentioned, the usage is for off-planet situations. <span style="font-family: Cambria;"> ] (])</span> 13:05, 19 December 2024 (UTC) | |||
:::::Using Sol, Terra and Luna to refer to the Sun, Earth and Moon only happens if you write your entire article in Latin and in science fiction, not in regular science articles. They are capitalised though. Just as people write about a galaxy (one of many) or the Galaxy (the Milky Way Galaxy, that's our galaxy). The Solar System is also capitalised. ] (]) 10:38, 19 December 2024 (UTC) | |||
::::::The article says "Sol" is the "personification" of the sun. Google Image the term "old Sol" and you'll see plenty of images of the sun with a face, not just Sci-Fi stuff. And "Luna" is obviously the basis for a number of words not connected with Sci-Fi. Lunar orbit, lunar module, etc. And the term "terra firma" has often been used in everyday usage. ←] <sup>'']''</sup> ]→ 11:34, 19 December 2024 (UTC) | |||
::::::: And yet, if you ask 1,000 people "What's that big yellow thing up in the sky called?", you'll get 1,000 "the Sun"s and zero "Sol"s. Yes, in specialised contexts, Sol is used; but that doesn't justify saying our solar system's star "is called Sol" without any qualification, as if that were the normal, default term. It's not. -- ] </sup></span>]] 12:16, 19 December 2024 (UTC) | |||
:::::::::And after you've gotten that response, ask them why it isn't the "Sunner System". And why a sun room attached to a house isn't called a "sunarium". And why those energy-gathering plates on some roofs are not called "sunner panels". ←] <sup>'']''</sup> ]→ 14:22, 19 December 2024 (UTC) | |||
::::::::::What does that have to do with anything? The question was 'Is our star system ''officially'' called "Sol"?' (my emphasis). The answer is it is not. And that does not preclude other terms being derived from Latin ''sol'' (or, often enough, from Greek ''helios''), nobody denies that, it is irrelevant to the question. --] (]) 14:52, 19 December 2024 (UTC) | |||
:::::::::::The problem is that the OP's question contains false premises. One is the question of what the "official" name is. There is no "official" name. It's the "conventional" name. And the second part, claiming that "Sol" comes from Sci-fi, is demonstrably false. ←] <sup>'']''</sup> ]→ 15:05, 19 December 2024 (UTC) | |||
::::::::::::Then demonstrate (that the usage of "Sol" as a name for the Sun, in English, not its use to derive adjectives, originated outside of SF), with references. The original question does not even include any premises, with maybe the exception of "ubiquitous". --] (]) 15:18, 19 December 2024 (UTC) | |||
:::::::::::::"Is our star system officially called "Sol" , or is that just something that came from science fiction and then became ubiquitous? ". And the wording of your own question, just above, does not make sense. ←] <sup>'']''</sup> ]→ 15:24, 19 December 2024 (UTC) | |||
::::::::::::::Looking at Newspapers.com (pay site), I'm seeing colloquial references to "old Sol" (meaning the sun) as far back as the 1820s. No hint of sci-fi derivation. ←] <sup>'']''</sup> ]→ 15:32, 19 December 2024 (UTC) | |||
:::::::::::::::Great! Well done. --] (]) 15:41, 19 December 2024 (UTC) | |||
::::::::::::::::Feel free to box up this section. ←] <sup>'']''</sup> ]→ 15:52, 19 December 2024 (UTC) | |||
:::::::::::::The 1933 OED entry for ''Sol'', linked to above, gives several pre-SF uses, the earliest from 1450. --] 23:48, 19 December 2024 (UTC) | |||
::::::::::::::Yes, of course, but that's not surprising, is it? 15th century humanists, astrologers and pre-Victorian poets liked to sprinkle their texts with Latin words. But I don't think this is what the question is about. It's a matter of context, but it should be up to OP to clarify that. --] (]) 08:48, 20 December 2024 (UTC) | |||
:::::::::::::::It's not surprising, but the discussion was not whether the use of ''Sol'' in English texts is surprising, but whether it originated outside of SF. --] 10:52, 20 December 2024 (UTC) | |||
::::::::::::::::In my view, the question has a clear scifi bent, and that particular usage ("Where shall we go for our vacation? Alpha Centauri or Sol?") does not originate in the 15th century. The word is much older, of course it is, but the usage is not. In the 15th century people didn't even know that the Sun is just an ordinary star and could do with a particular name to distinguish it from the others. The connotations of ''sol'' were vastly different from what they are today and from what is implied in OP's question. Incidentally, the ] doesn't even define a name , although they recommend using capitalised "Sun". Certainly no "Sol" anywhere. --] (]) 12:04, 20 December 2024 (UTC) | |||
::::::::{{small|Does that make it a Sol-ecism? ] (]) 12:19, 19 December 2024 (UTC)}} | |||
:::::::::<small>More like a ]. Meaning a factory where suns are made. From Sol = sun, and ipso = facto. Thus endeth the entymogology lesson for today. Go in peace to love and serve whomsoever. -- ] </sup></span>]] 19:37, 19 December 2024 (UTC) </small> | |||
== Mountains == | |||
Does anybody know how many citations an article has been cited? I know there is a function on some website that allows people to track how many people have cited the article in their own articles as part of their references/citations/bibliographies. By the way, have there been documented cases where scientists harshly criticized their rivals' work, where both scientific teams are engaged in the same field and both want the glory of making some important distinguished landmark? I seem to recall a story in the field of chemistry about some guy who discovered Helium and then lost to the guy who discovered Hydrogen... or was it the reverse? I forget. ] (]) 14:19, 29 October 2013 (UTC) | |||
:To answer the first part of your question, the number of times a scientific publication is cited is the main criterion used to decide its quality and it is something academics are obsessed with. There are a number of ways find out see: for example or google "how many times has my article been cited" As for the second part - scientific rivalry often spills over into harsh criticism of one anothers' work, and the awarding of the ]s are often a great source of controversy as to whether the recipient really should have got the credit - see ]. <span style="text-shadow:grey 0.2em 0.2em 0.1em; class=texhtml">]</span> ] 14:37, 29 October 2013 (UTC) | |||
::I beg to differ that it is not academics who are obsessed with citation count, but the people who evaluate academics (for allocating university rankings, research funding, etc). I'm sure most academics would happily not care about such dubious measures but are forced to if they are to survive. ] (]) 23:17, 30 October 2013 (UTC) | |||
*If you look up an article on ], it will show you the number of citations and allow you to list the citing articles. The number is often not completely accurate -- if it is important, you should check through the list to make sure that each entry is legitimate. ] (]) 16:48, 29 October 2013 (UTC) | |||
::Google Scholar is a useful tool but it has the drawback that it only includes journals that have been indexed online. In some fields this can omit the majority of publications. ''']]''' 17:27, 29 October 2013 (UTC) | |||
Why there are no mountains on Earth with a height above 10,000 m? As the death zone is about at 8,000 m, and above 19,000 m, there is an Armstrong limit, where water boils at normal human body temperature, it is good that there are no more mountains higher than 8,000 km than just 14, but if there were hundreds of mountains above 9,000 m, then these were bad to climb. If there were different limits for death zone and Armstrong limit, would then there be possible to have higher mountains? I have just thought that, it is not a homework? --] (]) 22:29, 18 December 2024 (UTC) | |||
:The old standard was ], but in some way that I don't understand they made themselves so much of a pain in the ass for so many researchers to use (both in terms of interface and who was allowed access from where) that for a while they've seemed to have become more obscure. ] (]) 21:11, 29 October 2013 (UTC) | |||
:There are ] that are over 20km high. Given that some of those are on airless worlds, I don't think the air pressure has any bearing on it. ] (]) 22:57, 18 December 2024 (UTC) | |||
Fighting scientist? {{doi|10.1029/2011JE003880}} against {{doi|10.1029/2010JE003599}}. Or an old example: The discovery of thallium {{doi|10.1098/rsnr.1984.0005}}. The favorite one is ] and ] are no elements because the French chemist was heading the naming committee and not the Austrian chemist. The bloody fight about ] and the devastating resistance about ] are other examples.--] (]) 12:30, 30 October 2013 (UTC) | |||
:Multiple sources from web searching suggest the ''theoretical'' maximum height for mountains on Earth is around 15,000 m – the limiting factor is ]; the higher (therefore more voluminous) a mountain is, the more its weight causes the crust beneath it to sink. The actual heights of mountains are a trade-off between how fast tectonic movements can raise them versus isostatic sinking ''and'' how quickly they are eroded, and tectonic movements do not last for ever. See also ]. {The poster formerly known as 87.81.230.195} ] (]) 00:25, 19 December 2024 (UTC) | |||
:If your German is good enough just read what ] wrote about his colleagues in his journal (one example of many is {{doi|10.1002/prac.18820260121}}).--] (]) 12:33, 30 October 2013 (UTC) | |||
::And erosion goes faster as the mountain gets higher, in particular when it's high enough to support glaciers – one reason why mountains can get higher on an airless world. Now it gets interesting for a mountain high enough to reach into the stratosphere, as it would be too dry to have anything but bare rock. I suppose it would locally raise the tropopause, preventing that. ] (]) 11:13, 19 December 2024 (UTC) | |||
::My German is extremely poor. A translation of the document or a summary written in English would be helpful. Thanks. ] (]) 15:55, 30 October 2013 (UTC) | |||
= December 19 = | |||
:::"...] is an excellent experimentor, but he is only an empiricist, lacking sense and capability, and his interpretations of his experiments show particular deficiency in his familiarity with the principles of true science..." To make it clear 1905 Baeyer was awarded the Nobel Prize in Chemistry.--] (]) 19:01, 30 October 2013 (UTC) | |||
== Does human DNA become weaker with each generation? == | |||
= October 30 = | |||
As with photocopying something over and over, the text becomes less clear each time. | |||
== The term for the tendency for dominant entities to get more dominant == | |||
Does human DNA become weaker with each generation? ] (]) 21:22, 19 December 2024 (UTC) | |||
Like Microsoft, planets, armies, wealthy individuals, etc. Being big helps them get bigger. Is it a maths thing? It seems to be everywhere. It seems that on Earth, it's fueled by money, and people jump into exploit the phenomenon. It seems to have a runaway effect. What's the term? It there one? ] (]) 05:13, 30 October 2013 (UTC) | |||
:Sure, DNA replication is not perfect, although ] reduces the error rate to about 1 mistake per 10<sup>9</sup> nucleotides (see our article on ]). But that is per generation of cells, not of the whole organisms. Many mutations will be neutral in effect (because much of our DNA is redundant), some will be deleterious, and a few might be advantageous. It is the process of natural selection that hinders the spread of deleterious mutations: sometimes this aspect is called ]. One thus usually expects a stable ] over time rather than that "DNA becomes weaker with each generation". Medical science is reducing the selection pressure against some mutations, which consequently may become more common. One of the problems for asexual organisms is referred to as ]; assuming that reverse mutations are rare, each generation has at least the mutational load of its predecessor. In contrast, in sexual organisms ] generates the variation that, combined with selection, can repair the situation. Sexual organisms consequently have a lighter genetic load. ] (]) 22:42, 19 December 2024 (UTC) | |||
::So ] won't work properly in case of ] ? ] (]) 23:16, 19 December 2024 (UTC) | |||
:::The larger the degree of inbreeding, the larger the chance that deleterious traits are expressed. But this very expression of traits leading to decreased biological fitness of their bearers is what actually enables purifying selection in the longer term. --] 23:36, 19 December 2024 (UTC) | |||
::::@] so ] won't stop these deleterious traits to get expressed? ] (]) 14:11, 20 December 2024 (UTC) | |||
:::::No, this is not an issue of ]. The genes involved are faithfully reproduced and passed on from generation to generation. --] 15:53, 20 December 2024 (UTC) | |||
:Or stronger e.g. "", and those guys live for centuries and have much more DNA than us. ] (]) 15:21, 20 December 2024 (UTC) | |||
::@] If not due to DNA damage, why do babies from inbreeding appear like DNA-damaged species? ] (]) 17:29, 20 December 2024 (UTC) | |||
:::Inbred offspring of species that normally outcross may show abnormalities because they are more likely than outcrossed offspring to be ] for ] that are deleterious. In individuals that are heterozygous at these loci, the recessive alleles will not be expressed (because the other wild-type dominant allele is sufficient to do their job adequately). See our article on ]. ] (]) 19:26, 20 December 2024 (UTC) | |||
== Larvae going south == | |||
Oh, and thank you, by the way. :) ] (]) 05:18, 30 October 2013 (UTC) | |||
In a novel I've just finished ('']'' by ]) he writes: | |||
:Well, the opposite and ultimately triumphant tendency is ]. - <span style="font-family: cursive">]</span> 06:27, 30 October 2013 (UTC) | |||
* '' leave the body in an orderly fashion, following each other in a neat procession that always heads south. South-east or south-west sometimes, but never north. No-one knows why''. | |||
The author has done considerable international research on the science of forensic identification of decayed bodies and I assume his details can be trusted. | |||
:]. ] (]) 06:58, 30 October 2013 (UTC) | |||
I've looked online for any verification of this surprising statement, but found only , which seems to debunk it. | |||
:I'm not 100% certain what it is you are looking for, so here's a bunch of things that might be of interest: ], ], ], ], ], ], ], ]. Do any of these fit the bill for the type of thing you are looking for? If so, I can help you find more specific details; or if not, what is missing (so i can narrow it down)?] (]) 07:30, 30 October 2013 (UTC) | |||
Is there any truth to this? -- ] </sup></span>]] 23:38, 19 December 2024 (UTC) | |||
::Wow! Holy moly! Yes, it's all of those, somehow. Those are some of the most interesting articles I've ever seen. I'm just getting started on them and it will take me a while. Thank you very, very much! | |||
:Can't speak to its truth, but . . . | |||
::Okay, I will return the favour. Here's something I made up: Tell a friend you can make a specific word come to mind. Write down "What???" on a bit of paper and fold it up. Then ask your friend: "Okay, ready? Are you sure? Okay, concentrate. Now, think of an animal between one and ten." ] (]) 08:09, 30 October 2013 (UTC) | |||
:* Does Beckett state this in his own auctorial voice (i.e. as an ])? If so, he might be genuinely mistaken. | |||
:* The book was published nearly 20 years ago, what was the accepted wisdom ''then''? | |||
:* What specific species (if any) is the book describing? – your linked Quora discussion refers only to "maggots" (which can be of numerous species and are a kind of larva, but there are many others, including for example ]). | |||
:*Alternatively, if the statement is made by a character in the book, is that character meant to be infallible, or is he portrayed as less than omniscient, or an ']'? | |||
:Regarding the statement, in the Northern hemisphere the arc of South-east to South-west is predominently where the Sun is found well above the horizon, the North never, so the larvae involved might simply be seeking maximum warmth or light. {The poster formerly known as 87.81.230.195} ] (]) 02:18, 20 December 2024 (UTC) | |||
:: This appears in the very first paragraph of Chapter I, which starts out: | |||
:::No problem:-) I'll dig around when I get home and see if I can find something with more details. --I like your trick, I'm going to use it at work:-)] (]) 08:15, 30 October 2013 (UTC) | |||
::* ''A human body starts to decompose four minutes after death. Once the encapsulation of life, it now undergoes its final metamorphoses. It begins to digest itself. Cells dissolve from the inside out. Tissue turns to liquid, then to gas. No longer animate, the body becomes an immovable feast for other organisms. Bacteria first, then insects. Flies. Eggs are laid, then hatched. The larvae feed on the nutrient-rich broth, and then migrate. They leave the body in an orderly fashion ...'' (then the quote above completes the paragraph). | |||
::::Where someone might respond, "Between one and ten ''inclusive'' or ''exclusive?''" ←] <sup>'']''</sup> ]→ 09:48, 30 October 2013 (UTC) | |||
:: It's not until para 2 that he starts talking about any human characters, and not until para 4 that he invokes the first person. | |||
:::::Or another wise guy might say, "Three-toed sloth." ←] <sup>'']''</sup> ]→ 09:51, 30 October 2013 (UTC) | |||
:: That's as much as I know. But I find it hard to believe he'd just make up a detail and put it in such a prominent place if it could so easily be debunked if it were not true. -- ] </sup></span>]] 02:39, 20 December 2024 (UTC) | |||
::::::Or they might say, "My dog." Then you say, "What?" And they say, "My dog just turned seven." ←] <sup>'']''</sup> ]→ 09:53, 30 October 2013 (UTC) | |||
::: |
:::I wonder how they would measure the migratory path of maggots within a sealed coffin. ←] <sup>'']''</sup> ]→ 02:51, 20 December 2024 (UTC) | ||
:::: The context of the novel is about finding decaying corpses that have been dumped in a forest. No coffins involved. -- ] </sup></span>]] 06:08, 20 December 2024 (UTC) | |||
::::::::At first I was confused. Then more confused. Then I finally got it. I think your friends think more than mine. Mine all just said "What???" :) ] (]) 11:16, 30 October 2013 (UTC) | |||
:] |
::::::], see also ] research facilities. ] (]) 13:44, 20 December 2024 (UTC) | ||
:::::Could it be that the larvae are setting off in search of another corpse? The prevailing wind in the UK is from the south-west, so by heading into the wind they won't be distracted by the frangrance of the one they've just left. ]|] 09:30, 20 December 2024 (UTC) | |||
If you can, have a look at 'Heinrich, Bernd. “Coordinated Mass Movements of Blow Fly Larvae (Diptera: Calliphoridae).” Northeastern Naturalist, vol. 20, no. 4, 2013, pp. N23–27. JSTOR, http://www.jstor.org/stable/43288173.' Here are some extracts | |||
:Money equates to power. Also described as, "The Golden Rule: Whoever has the gold, makes the rules." ←] <sup>'']''</sup> ]→ 09:46, 30 October 2013 (UTC) | |||
* On the fourth day, after a cooling night with dew on the grass, a stream of tens of thousands of larvae exited from beneath the carcass within 1 h after sunrise, and proceeded in a single 1-2-cm-wide column directly toward the rising sun... | |||
* However, in this case, the larvae left at night, within 1 h after a cloudburst (at 21 :00 hours). But, unlike before, this nocturnal larval exodus in the rain was diffuse; thousands of larvae spread out in virtually all directions over an 8 m2area. Apparently, the sudden moisture had cued and facilitated the mass exodus, but the absence of sun had prevented a unidirectional, en masse movement. | |||
* However, on the following morning as the sun was starting to illuminate the carcass on the dewy grass, masses of larvae gathered at the east end of the carcass at 07:00 hours. In one half hour later, they started streaming in a column directly (within one degree) toward the rising sun, and the carcass was then nearly vacated. | |||
It goes on. Maggot migration appears to be a bit more complicated than the novel suggests. ] (]) 09:39, 20 December 2024 (UTC) | |||
I suppose you could try to address it from the other direction and look at the technology your average maggot has access to in terms of light detection, heat detection, olfactory systems, orientation in magnetic fields (like many arthropods) etc. They presumably have quite a lot of tools. ] (]) 10:13, 20 December 2024 (UTC) | |||
:If orderly migrating maggots tend to move towards the sun, they should display a northward tendency in Oztralia. --] 10:31, 20 December 2024 (UTC) | |||
::Ah, another good article to absorb. Thank you. ] (]) 11:16, 30 October 2013 (UTC) | |||
:: Maybe, but the novel is set in England. | |||
:::See also ]. ] (]) 13:11, 30 October 2013 (UTC) | |||
:: I must say, as soon as I read the quoted para for the first time, my immediate thought was that it might have something to do with the magnetic field of the earth. -- ] </sup></span>]] 10:42, 20 December 2024 (UTC) | |||
::::It's important to realize that that "Golden Rule" assumes that everyone has at least some theoretical access to gold. If literally one guy had literally all the world's gold, then gold would be come worthless as money. ←] <sup>'']''</sup> ]→ 22:50, 30 October 2013 (UTC) | |||
:::Prime suspect might be the Bolwig organ, the photoreceptor cluster many fly larvae have. ] (]) 10:49, 20 December 2024 (UTC) | |||
:::Obviously, Jack, you need to create a corpse, place it in a nearby forest, and carefully observe which way the maggots go. For Science! And Literary Criticism! {The poster formerly known as 87.81.230.195} ] (]) 21:01, 20 December 2024 (UTC) | |||
= December 20 = | |||
:Economists like to call this ]. ] (]) 13:37, 30 October 2013 (UTC) | |||
== Winter solstice and time of sunrise? == | |||
:Another term is ]. Our article is strictly about the nuclear sense of the term, but it also has broader meaning similar to "tipping point". ] (]) 15:07, 30 October 2013 (UTC) | |||
How is it that despite December 21st supposedly being the shortest day of the year, sunrise here happens later and later until December 26 and only on January 05 starts to turn around to occur earlier and earlier. On December 25 it takes place at about 08:44, between December 26 and January 04 it takes place at about 08:45, and on January 05 it takes place again at about 08:44. (Google rounds out the seconds). Is it Google's fault? Is it everywhere the same? Confused in Brussels, Belgium. ] (]) 12:06, 20 December 2024 (UTC) | |||
:And, another important concept is that all such effects only operate within a certain range. That is, we don't have one person or company that owns everything, on nation that is able to conquer the world, one animal which replaces all the rest, etc. The reason is that at some point a significant ] also kicks in. In the case of business, this leads to a specific ]. In another field, you also get a stable population size for a given species, even a very successful one. I don't think even ]s are expected to contain the entire universe, due to ] and other effects. ] (]) 15:07, 30 October 2013 (UTC) | |||
:The pertinent article is ], start with the section ]. The details are not that simple to understand, but it's basically due to the ellipticity of Earth's orbit and its axial tilt. --] (]) 12:22, 20 December 2024 (UTC) | |||
::Also note that sunset begins to be later on 22 December so that the time between sunrise and sunset is a few seconds longer than on 21 December (3 seconds longer on 22/12/24 in Brussels according to ). ] (]) 13:33, 20 December 2024 (UTC) | |||
::Also see ]. The obliquity of the ecliptic (that is, the Earth's axial tilt) is the main component and hardest to understand. But the idea is that the time when the Sun is exactly south (that is, the true noon) moves some minutes back and forth throughout the year and it moves quite rapidly to later times in late December. ] (]) 19:05, 20 December 2024 (UTC) | |||
== Three unit questions == | |||
:And we'll throw in ] for a bit more abstract mathematical fun. ](]) 15:52, 30 October 2013 (UTC) | |||
# Why territorial waters are defined by nautical miles instead of kilometers? | |||
And I'll throw in ] - the nature of consumers to gravitate toward the most established product/service providers (applies more to some industries than others). ] (]) 22:51, 30 October 2013 (UTC) | |||
# Why GDP is usually measured in US dollars rather than euros? Euro would be better because it is not tied into any country. | |||
# Are there any laws in United States that are defined by metric units? | |||
--] (]) 23:30, 20 December 2024 (UTC) | |||
:#There were nautical miles in use before there were kilometers. | |||
:#There were US dollars in use before there were Euros. | |||
:#Yes. | |||
:The questions all reduce to Why can't millions of people make a change of historically widely accepted units that continue to serve their purpose, and convert to different units that would have no substantive difference, because someone has an opinion. ] (]) 00:52, 21 December 2024 (UTC) | |||
::Do any people use metric units in marine and air navigation like "The ship is 10 kilometers from the port", "The plane is 10 kilometers from the destination? And is there any European country with metric flight levels? --] (]) 07:22, 21 December 2024 (UTC) | |||
:::Inland shipping (rivers, canals and lakes) in Europe (except the UK) is fully metric. Ships going for example ] – ] may have to switch units along the way. Gliders and ultralight aircraft in Europe often use metric instruments and airport dimensions are also metric (including runway length). Countries are free to define their territorial waters in whatever way they deem fit, so with nautical miles having no legal status in a fully metric country, they may define their territorial waters as extending 22224 metres. ] (]) 11:23, 21 December 2024 (UTC) | |||
::::Our ] article says: {{xt|"In 1929 the international nautical mile was defined by the First International Extraordinary Hydrographic Conference in Monaco as exactly 1,852 metres (which is 6,076.12 ft). The United States did not adopt the international nautical mile until 1954. Britain adopted it in 1970..."}} | |||
::As the US customary units are actually defined in terms that relate them to metric units, any US law based on measurements is technically defined by metric units.--] (]) (]) 01:55, 21 December 2024 (UTC) | |||
:::The US dollar has been the world's dominant ] for about 75 years. As for the metric system in the US, it is standard in scientific, medical, electronics, auto manufacturing and other highly technical industries. By law, all packaged foods and beverages have metric quantities as well as customary quantities. See ]. ] (]) 02:28, 21 December 2024 (UTC) | |||
The Wikipaedia article on the Nautical Mile talks about how the term originated, it was originally defined in terms of latitude not as a number of meters ] (]) 10:03, 24 December 2024 (UTC) | |||
= December 24 = | |||
I'm going to toss into the ring. Not strictly examples of this phenomenon, but interesting and related nevertheless. More generally it sounds like you would be interested in reading about ]. If so I can highly recommend the series of books by ] entitled "Nature's Patterns, A Tapestry in Three Parts" ]<small> (] | ])</small> 23:50, 30 October 2013 (UTC) | |||
== Unknown species of insect == | |||
:I'm absolutely astonished at how much great content there is on this sort of thing. And all these articles get tons of page visits. Misplaced Pages builders are gooooooooooood. ] (]) 00:01, 31 October 2013 (UTC) | |||
Am I correct in inferring that ] this guy is an ]? I was off-put by the green head at first, but the antennae seem to match. ''']]''' 03:00, 24 December 2024 (UTC) | |||
== Heisenberg's delusion of adequately well behaved standard reality? == | |||
(reference: https://www.genesdigest.com/macro/image.php?imageid=168&apage=0&ipage=1) | |||
If you used ] to open the impenetrable cardboard box and dump ] into a region governed only by classical physics, wouldn't the poor beast die instantly in the flash of an ]? | |||
:<s>It looks like one of the invasive ]s that happens to like my blackberries in the summer.</s> ] (]) 13:11, 24 December 2024 (UTC) | |||
I.e. what color of wallpaper is used to paper over the cracks of the run down and condemned poorhouse where classical physics has been left to die in when the physicist makes some sort of effort to separate herself from quantum reality by suggesting that the padded room she's in is not part of all that quantum weirdness "out there"? Is there a well defined "classical model" that actually works, or is it all just Heisenberg's delusion of adequately well behaved standard reality, that breaks down if you poke at any of the walls? ] (]) 13:19, 30 October 2013 (UTC) | |||
::I would say not necessarily a Japanese beetle, but almost certainly one of the other ] beetles, though with 35,000 species that doesn't help a lot. Looking at the infobox illustration in that article, 16. & 17., "]" looks very similar, but evidently we either don't have an article or (if our ] article is a complete list) it's been renamed. {The poster formerly known as 87.81.230.195} ] (]) 14:18, 24 December 2024 (UTC) | |||
:If I not misunderstood your question, some model of a "classic" can be - The movement of the particles back and forth in time many times. Therefore statistics, Therefore possibilities, Therefore the "reality" stabilizing on part of the particles, so the "universes" are multiple . thanks Water Nosfim <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 14:06, 30 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
: |
:::Yes, it's not the Japanese beetle for this beetle appears to lack its white-dotted fringe although its condition is deteriorated. Its shape is also more or less more slender; and not as round. ] (]) 15:02, 24 December 2024 (UTC) | ||
:Perhaps it is the ] ]. Shown . ] (]) 16:09, 24 December 2024 (UTC) | |||
:The real question is how classical physics emerges as an approximation of quantum physics in a certain limit. (Just as relativistic kinematics reduce to Newtonian for low relative speeds.) This is a thorny question. The short answer is ], which explains why we see an adequately well behaved standard reality in which interference effects, superposition, etc. are not obvious. It's not that some systems are fundamentally classical instead of quantum, it's just that classical physics is a good enough description of some things and not others. --] (]) 19:45, 30 October 2013 (UTC) | |||
::That looks like easily the best match I've seen so far, and likely correct. {The poster formerly known as 87.81.230.195} ] (]) 17:09, 24 December 2024 (UTC) | |||
= December 25 = | |||
:For that matter, much of the ] is just pure nonsense, honestly, having done far more harm than good to the advancement of scientific thought. Ideas of ], ], and ] continue to spur us on into research of fictitious "]" and the like...meanwhile we just drift further and further from, well, reality. Go figure. ] (]) 07:23, 31 October 2013 (UTC) | |||
::Superposition, entanglement, and quantum computers are in no way dependent on the Copenhagen interpretation. --] (]) 08:37, 31 October 2013 (UTC) | |||
:::Let me rephrase that: the vast majority of ''Copenhagen-like interpretations'' are pure nonsense. More specifically, they all arise from a misinterpretation of the implications of probability with respect to physics; rather than seeing it as the mere necessity to consider all of the probabilistic "degrees of freedom" inherent in a system, they instead take the analogy too far, as it were, constructing a sort of ] ] ] of ] in the process. Quantum computers are a direct result of such interpretations and thus nothing more than an interesting thought experiment. ] (]) 15:53, 31 October 2013 (UTC) | |||
::::That's quite a tangle of misconceptions. --] (]) 18:12, 31 October 2013 (UTC) | |||
:::::You may be surprised to find that ]. But hey - what could ''they'' possibly know about all that? ] (]) 19:49, 31 October 2013 (UTC) | |||
::::::Thanks, but I'll take modern experimental and theoretical work in quantum information over a local hidden variables interpretation that has been shown to be inadequate many decades ago. And I have no idea why you believe that quantum computers depend on any particular interpretation of quantum mechanics. They don't. --] (]) 20:16, 31 October 2013 (UTC) | |||
::::::::] is the relevant article, although the experiments are unlikely to convince the OP. ] (]) 21:45, 31 October 2013 (UTC) | |||
:::::::::Bell's experiments have ] and besides that don't in any way invalidate what I have said. You '''can''' use quantum equations without having to accept that they are inherently "real" (just as you can use probability in many other fields without having to draw any such conclusions). ] (]) 22:34, 31 October 2013 (UTC) | |||
:::::::They most certainly do. To quote the first line of ], in fact: | |||
::::::::"A quantum computer (also known as a quantum supercomputer) is a computation device that makes direct use of quantum-mechanical phenomena, such as '''superposition''' and '''entanglement''', to perform operations on data". | |||
:::::::Superposition and entanglement are merely (the Copenhagen-type variety of) interpretations of the ''possible implications'' posed by the equations used in quantum mechanics. Furthermore, from the first line from ]: | |||
::::::::"Quantum superposition is a fundamental principle of quantum mechanics that holds that a physical system—such as an electron—exists partly in all its particular theoretically possible states (or, configuration of its properties) simultaneously; but when measured or observed, it gives a result corresponding to only one of the possible configurations (as described in ''']''')". | |||
:::::::Finally, from the article on ]: | |||
::::::::"Quantum entanglement is a product of '''quantum superposition'''.". | |||
:::::::So you see, all of these ideas are indeed connected. It's no wonder people like ] are so much more popular than ] in this day and age - science has become a mythological free-for-all, sadly... ] (]) 21:04, 31 October 2013 (UTC) | |||
:::::::: To the extent that the theories are predictive and validated by experiment, they are valuable models. Mathematical models describe what we observe. To the extent quantum mechanics lends itself to the description of observation (and the effect observation has on the experiment), is very well documented. I think everyone realizes that a description of a thing is not the thing itself. But if it's sufficiently detailed to predict behavior of the thing, then it's a pretty good model. As far as I can tell, QM's basic premise is the observer is part of the system. Probabilities arise from the uncertainties introduced by the observer. Superposition for example, describes all the observable states for an electron. It's a useful description and model but we can't create an electron from it. We also can't observe a state not part of the superposition description nor can we violate some of the fundamental underpinnings. Until that happens, it's a pretty good model. --] (]) 23:33, 31 October 2013 (UTC) | |||
:The crux of the problem is are you trying to determine the state of the cat without measuring it? --] (]) 07:33, 31 October 2013 (UTC) | |||
Put the cat back in the box and measure the observable O = |dead><alive| + |alive><dead|. ] (]) 16:04, 31 October 2013 (UTC) | |||
== Division by nothing == | |||
I know that division by zero is not mathematical, but what do you get if you divide something with nothing? <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 13:22, 30 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
By this mean insted of 5/0 trying for to do example 5/ <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 13:23, 30 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
::According to quantum physics, there is no nothing, so division is well bounded. Alternatively, you can roll up the ] into the ] by adding an infinity point, giving a result for every use of the division operator. ] (]) 13:28, 30 October 2013 (UTC) | |||
:::Not sure this is a science question more a maths one. But this has a good explination. Zero and nothing are the same thing.] (]) 13:59, 30 October 2013 (UTC) | |||
*It depends on the system you are operating in. In most programming languages, "5/0" will give you a <code>floating point exception</code>, whereas "5/" will give a <code>syntax error</code> when you try to compile the program. ] (]) 14:36, 30 October 2013 (UTC) | |||
::Looie496's answer is excellent - because at the core, our original question is not well-defined. In English, we use the word "division" to refer to many related mathematical concepts, including the calculation of the ] and the ] by the adjoint or conjugate. In these cases, we can explicitly define a mathematical result. If you use a programming language to ask the question, you are forced to be very specific; and depending on what you ask, we can provide the result. In English, your words leave enough ambiguity about your intent that we can't answer very specifically. | |||
::Speaking of programming - I recently did battle with the innards of a mathematical representation in the C++ ]. I was winning the battle, but I realized I had lost the war when I discovered that my predecessor had overloaded arithmetic operations, including <tt>/</tt>, as ]s so that he could divide by nothing while iterating over empty sets. I saw red-links, and knew I had crossed over the edge of reason and had reached the limit of human knowledge. ] (]) 15:57, 30 October 2013 (UTC) | |||
http://en.wikipedia.org/Division_by_zero ] (]) 14:56, 30 October 2013 (UTC) | |||
You have lack of information about the denominator, so the outcome fo the division is not known. But what you can say is that the amount of information about the outcome will increase by | |||
2 <Log|x|>, where you have to average over all possible inputs. ] (]) 15:53, 30 October 2013 (UTC) | |||
:What the OP is calling "nothing" is actually the "]". Any computer language worth its salt will have a trap for undefined operations like that. I tried it in Oracle SQL, and 5 over null is... surprise! ...''null''. ←] <sup>'']''</sup> ]→ 16:38, 30 October 2013 (UTC) | |||
:The question is not answerable. The OP admits that division by zero is not defined, but then asks what happens when you do it. It's not that it is forbidden, it's simply not defined. Some calculators/computers will raise some type of error that you could catch, like any other logical error. However, you ] ] (]) 19:46, 30 October 2013 (UTC) | |||
:::Division by zero is well-defined in some contexts — see our article on ] for a discussion, or go straight to ] for the most important example. But what "division by nothing" is supposed to mean, I'm not sure. Zero is a thing, and the empty set is also a thing, so neither of them is "nothing". Maybe it's more of a language question? If you divide five by nothing, literally speaking, you just didn't do anything, so there is no result of this action, because there wasn't any action. --] (]) 19:56, 30 October 2013 (UTC) | |||
::::In that sense, it's no different from dividing 5 by an apple. That doesn't work either. Most computers and calculators nowadays will pre-empt division by 0 and flag it as an error. But I recall a few decades ago, a mechanical calculator. If you divided X by Y, it would compute it, apparently by figuring out what Z x Y would equate to X. All well and good, until you divided 1 by 0. Then it would start calculating the Z value mechanically. Basically it would just start counting up. The machine had maybe 15 or 20 digits, and although it seemed to be going pretty fast, each power of 10 would naturally take 10 times as long to switch to the next high-order digit as did the next lower-order digit. I figured it would have to have run for days or maybe weeks before it would hit the last digit. So I stopped that experiment, and never did learn what would have happened once it reached all 9's. ←] <sup>'']''</sup> ]→ 22:43, 30 October 2013 (UTC) | |||
:::::Well, no, it is different. Dividing 5 by an apple doesn't make sense, but it could make sense if you specified what new meaning of "divide" you have in mind. Similarly with dividing by zero (though there well-established meanings already exist) or dividing by the empty set (where they don't, as far as I know) — those are both ''things''. But the word "nothing" does not refer to a thing; it has a different linguistic function altogether. --] (]) 22:47, 30 October 2013 (UTC) | |||
I think the short, complex answer is ''infinity''. Division by zero is undefined in the real number system, but in Calculus and other higher math, we can argue it is conceptually equal to infinity. Or we might say, "approaching infinity" since it cannot be reached. In other words, how many times does 0 go into some finite number? Infinite number of times. - ] (]) 01:59, 31 October 2013 (UTC) | |||
. ] (]) 02:06, 31 October 2013 (UTC) | |||
*Let me just say Hcobb's answer is no, good. Concepts are not physical objects, no more than motherhood has a molecular weight. The statement is a category error. ] (]) 02:31, 31 October 2013 (UTC) | |||
Division by nothing produces the IP address 128.214.166.7, if you want it to. The word "]" in mathematics would most commonly mean "0", but not necessarily, and even what "0" means depends on the context. More importantly, the expression "5/" by itself or more generally "x/" by itself doesn't have any well-established mathematical meaning. So by talking about "x/" you're creating new mathematics (which is a perfectly legitimate thing to do), and you're free to define what you mean by "x/" without it even causing confusion due to your meaning being different from some usual meaning of that expression. In particular, you're free to define a function called "division by nothing", which is denoted by the symbol "/" using ] , such that <math>/ \colon \mathbb{R} \rightarrow \mathbb{IP}</math>, where <math>\mathbb{R}</math> as usual means the set of reals and <math>\mathbb{IP}</math> means the set of IP addresses, and for all x, x/ = 128.214.166.7 . I'm not a mathematician, so a professional mathematician might express the definition of the function a little better than I did, but my point is that you're free to define what "division by nothing" means however you want to. ] (]) 03:10, 31 October 2013 (UTC) | |||
::::"The word nothing in mathematics would most commonly mean 0"? No. Where do you get that? 0 is very definitely something; it is absolutely not nothing. --] (]) 03:40, 31 October 2013 (UTC) | |||
:::::Well, the word "nothing" is certainly sometimes used in mathematical contexts to mean zero; here is the title of an article in Scientific American, as well as the title of book written by a mathematician, that uses "nothing" to mean "zero". The word is also sometimes used to mean the empty set. The word is also sometimes used to mean neither of those things. The whole point of my sentence is that the meaning of the word "nothing" depends on the context. There is no established context I'm aware of in which "division by nothing" is defined, so creating a new context in which it is defined doesn't conflict with any existing definition. ] (]) 04:51, 31 October 2013 (UTC) | |||
:::::::The subtitle in your link is just a witticism, not a genuine use of "nothing" to mean "zero". | |||
:::::::The thing is that ''nothing'' is used as a noun phrase, but it is not interpreted as having a referent; when it appears in a sentence, it's normally to be interpreted as the universal quantification of a negative statement. "I saw nothing" doesn't mean "I saw x, which is nothing"; rather, it means "for every x, I did not see x". So if you divide by zero, you may or may not get a definite answer, depending on the context. But if you divide by nothing, you just don't divide by anything. --] (]) 08:26, 31 October 2013 (UTC) | |||
::::::::Perhaps the article subtitle can be dismissed as a witticism, but the book title "The Nothing that Is: A Natural History of Zero" mentioned in the article isn't just using a witticism as far as I can tell. But I think it's all moot, because I think the term "nothing" is only used in very informal mathematical contexts, and mainstream math doesn't have a rigorous concept called "nothing". At least, ] doesn't list any possible meaning other than zero or the empty set, and I think in formal settings mathematicians would use one of those two terms instead of "nothing", when they want to talk about zero or the empty set. If you're aware of a reliable source containing a rigorous mathematical treatment of "nothing" as being defined as something other than zero or the empty set, please give a citation, so that the ] section can be updated. ] (]) 09:51, 31 October 2013 (UTC) | |||
:::::::::Of course there is no "rigorous mathematical treatment of 'nothing'". That's the whole point of what I was saying — the word "nothing" looks syntactically like something that should have a referent (because it constitutes a noun phrase), but in the actual ''semantics'' of the English language, it serves a different function and does not have a referent. So there ''can't'' be a mathematical (or, indeed, any) treatment of it, because there is no "it". --] (]) 20:26, 31 October 2013 (UTC) | |||
::::::::::I think I see your point, and I agree with what I think your point is. The English sentence "I saw nothing" means something like "the number of objects that I saw was zero", or "the set of objects that I saw was empty", not "I saw the number zero" or "I saw the empty set". Similarly, the phrase "division by nothing" means something like "the number of numbers being divided by is zero", or "the set of numbers being divided by is empty", not "division by zero" or "division by the empty set". That's consistent with my treatment of the "division by nothing" function above. The function in question is a function that has one argument that's labeled as being a "numerator", and zero arguments that are labeled as being a "denominator", not a function which has one "numerator" argument and one "denominator" argument whose value is zero, or whose value is the empty set. ] (]) 22:09, 31 October 2013 (UTC) | |||
:It simply doesn't make sense to not have a denominator, it's a non-function. It is possible to have the denominator as undefined, but must still be something. ] (]) 03:19, 31 October 2013 (UTC) | |||
::The "division by nothing" function I defined has a domain of <math>\mathbb{R}</math>, not <math>\mathbb{R} \times \mathbb{R}</math>. I.e., the "division by nothing" function doesn't have a denominator, by definition. ] (]) 03:55, 31 October 2013 (UTC) | |||
:::You've got it wrong, the domain is <math>\mathbb{R} \times</math>, not <math>\mathbb{R}</math>. ] (]) 04:07, 31 October 2013 (UTC) | |||
:::'''ERROR''': Parsing failure (EXPECTED OPERAND). ] (]) 06:16, 31 October 2013 (UTC) | |||
::::It doesn't make sense for the expression "x/" to not have a denominator, if the symbol "/" in that expression is referring to the standard division function whose domain is <math>\mathbb{R} \times \mathbb{R}</math>. But that doesn't mean that somebody can't define a new function that uses the same symbol, whose domain is just <math>\mathbb{R}</math>. And if the domain is just <math>\mathbb{R}</math>, and the symbol for the new function is defined as being used after the function's argument (similar to x! for the ] function), then the expression "x/", where <math>x \in \mathbb{R}</math>, is perfectly well defined for that new function. ] (]) 06:21, 31 October 2013 (UTC) | |||
:::::Well, that is bit a useless answer. The OP has already defined / as division. You're basically saying, that hypothetically, if you had a million dollars, then you would have a million dollars. It is a self-evident statement, which has no real bearing on the OP's question. ] (]) 07:24, 31 October 2013 (UTC) | |||
:::::Baseball, the empty set is no equivalent to nothing. Nothing has no mathematical definition, or any definition for that matter, the empty set is by no means equivalent to nothing - the empty set is a useful mathematical tool. | |||
::::::The OP most certainly has not defined "/" as being the normal division function. The normal division function is defined as a function whose domain is <math>\mathbb{R} \times \mathbb{R}</math>. But the OP has explicitly specified that the "division" function being referred to does not involve a denominator of zero. The "division" function being referred to also doesn't have a denominator that's a non-zero real, either; the expression "5/" only shows the function as having one argument, i.e., it doesn't have any kind of denominator (i.e. second argument) at all. It's possible to define a new function that meets the OP's criteria, but none of the standard functions called "]" do. ] (]) 09:23, 31 October 2013 (UTC) | |||
:::::::Where has the OP given this liberty to redefine division? ] (]) 21:27, 31 October 2013 (UTC) | |||
::::::::My first post above, at 03:10 31 October 2013, points out to the OP that ''if '''he''' wants to, '''he''''' can take the liberty of choosing to define "division by nothing" in such a way that his question makes sense, without conflicting with existing mathematics. The function I supplied was merely an example of a function that would work for that purpose. The question is not consistent with the normal division function whose domain is <math>\mathbb{R} \times \mathbb{R}</math>. If an alternative function is not considered, then the question has no more meaning than "what is the square root of a unicorn?" ] (]) 23:17, 31 October 2013 (UTC) | |||
: this is more of a mathematics function. Often the answer depends not on the fixed number division, but rather whether the numerator converges faster or slower to 0 than the denominator. --] (]) 07:18, 31 October 2013 (UTC) | |||
== Drinking Ethanol, does it makes you live longer? == | |||
I have seem to be found very contradictory claims on alcohol (as a popular beverage) where it says that drinking it will make you live longer, or have healthier life, other claims that drinking alcohol, is bad for health, and should be avoided at all costs. | |||
There doesn't seem to be a consensus about it, so is it really true that drinking alcohol makes you live longer, or it's just a myth? Thank you. ] (]) 17:29, 30 October 2013 (UTC) | |||
:You may be interested in our articles ] and ]. It is true that some studies have found that regular ''moderate'' consumers of alcohol (or sometimes specifically wine) seem to live longer, or gain other health benefits. It should also be obvious from the first article that ''excessive'' alcohol consumption over a long period of time seems to be extremely bad for you. So the conclusion is less "avoid at all costs" and more "everything in moderation". But you have to keep in mind that most of these long-term studies are looking at correlation only, and ]. ] (]) 17:57, 30 October 2013 (UTC) | |||
::Note that the studies on wine of which I am aware do not cite ethanol as the beneficial substance, but rather other compounds found in wine (see the article cited above for more information) ]<small> (] | ])</small> 23:34, 30 October 2013 (UTC) | |||
::<small> Of course excessive consumption in bad for you, that's pretty much the definition of excessive consumption - "the amount which is bad for you" ] (]) 09:40, 31 October 2013 (UTC) </small> | |||
:And the big difference is what you would be drinking, otherwise. If soda, especially soda with artificial sweeteners, then a bit of alcohol is a favorable alternative. ] (]) 21:55, 30 October 2013 (UTC) | |||
::Yeah, if instead of ethanol you decide to drink methanol you'll live a much shorter life. ] (]) 22:02, 30 October 2013 (UTC) | |||
:::''"especially soda with artificial sweeteners"''? Excuse me? citation please... ], , ] (]) 23:40, 30 October 2013 (UTC) | |||
::::Well, you had a citation right in our Wikpedia article: . That concluded that diet soda and regular soda are equally unhealthy. However, they made the assumption that equal quantities were consumed, ignoring the fact that many will drink more diet soda, since they aren't as worried about the calories. When you factor that in, diet sodas are worse. ] (]) 01:38, 31 October 2013 (UTC) | |||
:::::A {{fact}} you say? Oh and speaking of needed citations, where's the one for the claim alcohol is preferable to soft drinks? The link you provided says nothing useful to either query. In fact it doesn't even say what you claimed it said. (It doesn't say they are equally unhealthy, it only says people who consumed diet drinks also had similar health risks and goes on to note the evidence is quite contentious and particularly mentions there are a bunch of confounding factors like people consuming diet drinks because they already had health problems, as μηδείς mentions below. I would also note since the study appears to be an ], it seems unlikely any 'assumptions' were made about equal consumption.) | |||
:::::] (]) 04:43, 31 October 2013 (UTC) | |||
::::::Try this one then: . ] (]) 05:01, 31 October 2013 (UTC) | |||
:::Actually, an antidote to methanol poisoning is ethanol. They compete for the metabolic pathways so it becomes a rate equation as to which wins. The liver clears both but too high of the intermediate metabolites can cause blindness and death for methanol but if you can reduce the rate of methanol metabolism and spread it out through the ingestion of ethanol, you may live and also see the benefits of a beer. The liver prefers metabolizing ethanol over methanol and keeps the intermediate toxins at bay. YMMV and don't try at home. --] (]) 08:00, 31 October 2013 (UTC) | |||
::::I imagine if they catch they methanol poisoning early enough, they would induce vomiting or pump the stomach. ] (]) 17:03, 31 October 2013 (UTC) | |||
*Can you give a mechanism as to why diet soda is worse? Wouldn't it simply make sent that people who drink diet soda do so in a significant part because they are already heavy or diabetic, hence a less healthy cohort? ] (]) 02:28, 31 October 2013 (UTC) | |||
:*I believe the suspected mechanism is as follows: Your body starts to produce insulin as soon as sugar is consumed, so it will be in place as it is digested, to prevent a blood sugar spike. However, artificial sugars fool your body into thinking you consumed sugar, so the insulin is still produced, causing your blood sugar to crash. Your body then responds to this by increasing your cravings for sugar. You then eat some real sugar. You thus suffer all the consequences of consuming sugar, plus the consequences of the blood sugar crash beforehand. ] (]) 04:59, 31 October 2013 (UTC) | |||
:The difficulty is that the studies that show that moderate amounts of alcohol are beneficial don't present an underlying mechanism. It's perfectly possible that, for example, people who drink "socially" are getting the benefit from being social - not from the actual alcohol...or that people who are naturally more healthy are happier than people who aren't, and are therefore more likely to drink moderately. It's very difficult to disentangle cause from effect here. ] (]) 05:59, 31 October 2013 (UTC) | |||
I know of one abstainer who admits that the only reason he is alive is because he used to drink enormous amounts of booze, it was that or top himself. So he reckons that despite the damage it did him, at least he is alive, 30 years later. (cite: Ross Fitzgerald in The Australian) ] (]) 23:35, 31 October 2013 (UTC) | |||
== Practically visible universe stops growing == | |||
When will that happen? The visible universe will grow forever (and never exceed 2.36 times the space) but all but our cluster will become too redshifted to detect. What's the real ratio then? <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 20:31, 30 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
:Eventually, there will likely be nothing left to detect at all; see ]. For a timeline of what will happen before then, see ]. And although there is a growing consensus that the universe will continue to expand forever, there are dissenting opinions; see ]. ] (]) 00:55, 31 October 2013 (UTC) | |||
: Long after you have died. You will either obtain the answer through divine intervention or simply cease to care. :) --] (]) 08:41, 31 October 2013 (UTC) | |||
== XENON-100 project regarding dark matter detection? == | |||
Is there any short description of the project? or if someone cares to convert the PhD publications into an wikipedia article.. I'm particulary interested in how they physically accomplish this. ] (]) 22:00, 30 October 2013 (UTC) | |||
:You have already ''found'' the short description of the project. "XENON is a next-generation Dark Matter Direct Detection experiment, which will use liquid xenon as a sensitive detector medium to search for WIMPs (Weakly Interacting Massive Particles)." If you are not familiar with ], the Misplaced Pages article may help. ] (]) 22:53, 30 October 2013 (UTC) | |||
::Makes me wonder if there's other methods to detect dark matter other than scintillation or WIMP. Perhaps like interaction with a field rather than with a mass.. ] (]) 23:02, 30 October 2013 (UTC) | |||
:::There are a variety of approaches to direct detection. (Note that WIMPs are a type of dark matter candidate, not a detection method.) Other channels are used to search for WIMPs: XENON-100 uses ionization and scintillation, and other projects also use phonons or heat. uses bubble nucleation. The ] looks for a different candidate, ]s, by searching for their interaction with the electromagnetic field in a cavity. --] (]) 00:43, 31 October 2013 (UTC) | |||
:We do already have an article for the Xenon family of experiments that includes Xenon100: ]. Funny that you ask about Xenon-100 on the day that ], a very similar but competing experiment, released its first results. --] (]) 06:23, 31 October 2013 (UTC) | |||
= October 31 = | |||
== Testing for Pink Noise == | |||
I am aware of statistical tests for white noise in a real signal (Box-Pierce, Ljung-Box tests) and red noise (Percival test) but am unaware of any statistical tests for pink noise in a signal and cannot find any literature on this, only properties of pink noise and the generation of pink noise. Does anyone know of any? <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 07:48, 31 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
:Articles related to ] have detection and elimination techniques. Suppressing flicker noise below the thermal noise floor is generally the goal. Double correlated sampling and chopper stabilization are techniques to move the flicker noise below thermal noise. detection is basically all 1/f noise is pink noise. --] (]) 08:11, 31 October 2013 (UTC) | |||
::I think it's important to point out the distinction between pink noise and flicker noise, which our articles don't make clear. Pink noise is any noise with a 1/f (3 dB per octave) ]. Flicker noise is a type of pink noise produced in electronic devices. The two terms aren't synonymous. ] (]) 22:14, 31 October 2013 (UTC) | |||
:::Flicker noise does from the description seem to resemble shoot noise but where every single electron contributes and thus it looks different but have the same base? ] (]) 23:39, 31 October 2013 (UTC) | |||
::::] has a white (frequency-independent) spectral density, not a pink (1/f) density. I'm afraid I don't understand the rest of your question. ] (]) 00:06, 1 November 2013 (UTC) | |||
== Agriculture and global food supply == | |||
Can you tell me what the current amount of staple foods needed for the world supply is? I want to know the amount of food produced for at least 3 staples and the total world population of those 3 staples.--] (]) 13:53, 31 October 2013 (UTC) | |||
*Is meat one staple, grain another staple, and fruits still another staple? | |||
*Also, if meat is one staple, does this mean that beef, mutton, pork, and chicken meat are all one staple?--] (]) 14:40, 31 October 2013 (UTC) | |||
:::I think you misunderstand the concept of a ]. There is never more than one staple in a given community with a common diet. --] (]) 18:31, 31 October 2013 (UTC) | |||
== World Population in 50 years == | |||
What is the projected increase in world population for the next 50 years? (If you can, give me a weblink, too.)--] (]) 13:55, 31 October 2013 (UTC) | |||
:] has a projection. ] (]) 14:09, 31 October 2013 (UTC) | |||
::So, we're looking at a world population of 10 billion in 2063.--] (]) 14:18, 31 October 2013 (UTC) | |||
== Trousers == | |||
Cuold you please explain me how wearing two trousers (or, in general, wearing multiple layers of clothes) produce warmth? | |||
Sorry for a stupid qestion, but I really don't know. --] (]) 14:44, 31 October 2013 (UTC) | |||
:This will trap a layer of air between the clothes, and air has a very low thermal conductivity coefficient. So, what then happens is that the same amount of heat that your body produces must still escape via your clothes, but this heat will escape from the top layer of your clothes, So at that top layer the temperature will be the same (because heat transfer depends on the temperature difference and the heat transfer between the top layer and the air will be the same). Then the hat transfer from your body to that top layer must also be the same in bith cases, but nowwith more air trapped between the top layer and your body, the tamperature difference must be larger, so the temperature at your skin will be larger. ] (]) 14:56, 31 October 2013 (UTC) | |||
::An air layer is part of the answer, but two layers of the same material also cuts in half the heat transferred by conduction through the fabric, and also decreases the flow of cold wind if the fabric is porous enough to allow any air current. ] (]) 18:55, 31 October 2013 (UTC) | |||
:Layers also provide another advantage: It's important to prevent sweat from building up, which can then make you very cold and uncomfortable later. With layers, you can add or remove layers as needed, to keep comfortable. If you had a single, thick item of clothing, you would lose this flexibility. ] (]) 16:49, 31 October 2013 (UTC) | |||
::This is probably clear, but just in case: Clothing doesn't produce any warmth, it is only your body that produces warmth. Clothes only reduce the heat loss of the body. You can wrap a stone in as many layers as you wish and it will not warm up.] (]) 22:41, 31 October 2013 (UTC) | |||
== RPG-29 == | |||
I have a curiosity about RPG-29 rocket: in its technical description is said that it could penetrate 750 mm of RHA (]) or 1500 mm of ]. This sound to me very strange: the reinforced concrete has a ] of 12-15 megapascal and the RHA of 1000-1200 megapascal (80 times higher). How it's possible so low difference beetwen the two penetration? Isn't maybe the data for RHA overstimed or there is any other reason? ] (]) 17:37, 31 October 2013 (UTC) | |||
:An RPG uses a ]. The liner of the charge is compressed into a narrow jet of metal moving at speeds up to 14 km/s. At those speeds, the strength of the armor plays a minor role, it's mainly the density or weight that determines how far the charge penetrates, that's why some tanks use depleted uranium in their armor. ] (]) 18:26, 31 October 2013 (UTC) | |||
:See also ], that mentions that fused silica glass had a higher stopping power than steel (not sure that can be explained by density). To defend against hollow (shaped) charges, ] has been developed: an explosion moves part of the armor while the jet of the shaped charge is penetrating, disrupting the shape of the jet and diminishing the penetrating depth. To defeat reactive armor, the ] and other HEAT rockets use two shaped charges, the first will trigger the explosive charge in the armor, the second strikes milliseconds later, when the armor isn't "reactive". ] (]) 19:13, 31 October 2013 (UTC) | |||
== 'Real world length contraction' moved to archives. Why? == | |||
I'm new here... wondering why discussion of my question "'Real World' Length Contraction" was deleted from the current menu and moved to the archives, while, for instance the "vomiting while pregnant" question and others remains on the up-front menu. Wherever I raise the question of a variously contracted Earth diameter, or contracted distances between stars... depending on all varieties of relativistic frames, I am either called a crank (and banned from science forums) or told that challenging mainstream length contraction is inappropriate... or the topic is hidden in the backwaters, like the archives here. Will someone here please explain why my question was brushed aside as above with no answer? Thanks <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 17:58, 31 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
I just asked about the above but forgot the headline... and the question disappeared. <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 18:04, 31 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
:Because questions 5 days old are archived automatically. ] (]) 18:12, 31 October 2013 (UTC) | |||
:If there's more you feel needs to be explored, feel free to open a new question along those lines. Ideally, don't just ask the ''same'' question (unless, say, no one responded at all), but focus on what you feel was not addressed. --] (]) 18:16, 31 October 2013 (UTC) | |||
Thanks. The question was left hanging at the challenge of a shrinking Earth diameter, depending on the velocity and direction of relativistic frames observing it. The muon question was also left unanswered. I'll open a new question on those cases of supposed contraction specifically. | |||
: The point is that you come over as quite hostile. You're essentially saying "I don't believe in Special Relativity - it's impossible" - which is not asking us a question. In fact, you're entirely wrong. Special relativity is true - it's one of the better tested scientific theories - and much of what happens in the universe can only be explained by it being true. People have gone so far as to measure the ticking of the clocks on actual, for real spacecraft to see if time is slowed for them - and it is. If you own a GPS unit - you may be surprised to know that there is software inside that little box that has to compensate for both special and general relativity in calculating where you are in the world. This stuff really isn't up for debate. | |||
: So we're telling you the answer - "The Truth". It's OK if you don't fully understand it - by all means, ask for clarification. But issuing "challenges" and being generally combative is hostile to our volunteer staff, who's mission here is to tell you the truth and explain it if you don't understand. We're not here to disprove or challenge whatever wonky ideas you may have of your own. If you wish to dismiss all of mainstream science on this point and ignore what 100% of the respondents here are telling you, that's fine - go away and be flat out wrong someplace else. But please don't argue with us. We're telling you the truth as researched most carefully by hundreds of people who were all a lot smarter than any of us here! | |||
: Subjects like relativity and quantum theory are strongly contrary to "common sense" - but that's not because they're wrong - it's because we humans have evolved in a world where nothing much moves anywhere near to the speed of light (except light) and all of the objects we deal with routinely are bigger by far than an atom. The "common sense" that we evolved as stone-age hunter-gatherers on the African plains is pretty much useless for explaining what goes on in realms that it did not evolve to handle...so we find it hard to get our heads around the reality of the universe at these crazy speeds and scales. I forget who said it, but: It's not natures' duty to be understandable by mankind. | |||
: Perhaps you'd do our volunteers the kindness of toning down your rhetoric - and rather than telling us that this is all wrong and impossible (which it's definitely not), confine yourself to politely requesting clarifications for the parts that you don't understand. Do that, and things will progress more smoothly. | |||
: ] (]) 21:38, 31 October 2013 (UTC) | |||
::I didn't read all that, but you apparently missed his question, the OP asked for an explanation or the underlying mechanisms regarding length contractions. Not that hard is it? --] (]) 00:17, 1 November 2013 (UTC) | |||
== Contracted Earth diameter and atmosphere depth == | |||
My "real world length contraction" question was moved to the archives (after the 5 day limit, I'm told... but doesn't seem to apply to other topics), so here are the unanswered challenges from that exchange: | |||
If a relativistic frame (future ship or whatever) approaches Earth in the direction of its axis at .866c, special relativity (SR) says that it will measure the polar diameter to be about 4000 miles. Then if it turns around and approaches at the same velocity in the direction of the equatorial diameter, that will now be measured as 4000 miles, and the polar diameter will have restored to its proper length just under 8000 miles. SR insists that all frames are equally valid, so then Earth must "morph" with every possible velocity and direction from which it could (relativistically) be observed. True of false? | |||
Muons traveling through our atmosphere have higher velocities than lab-accelerated muons, so they decay more slowly ("live longer") and therefore travel further than lab muons, so they can reach Earth's surface. SR claims that the depth/thickness of the atmosphere contracts "for those muons." But the atmosphere remains about 1000 km all around Earth at all times, not contracted by what incoming muons would "observe." Different observations can not change physical objects or distances. SR claims that it does. SR advocates now have another 5 days to reply to this challenge. <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 18:51, 31 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
: SR says that the squared invariant distance between two points in space-time (x,y,z,t) and (x',y',z',t') is | |||
: s^2 = (t-t')^2 - | |||
: where the time and the positions are measured in the same units (so the speed of light, is set equal to 1). So, SR disputes the validity of Pythagoras' formula and it disputes that time intervals are invariant. ] (]) 19:32, 31 October 2013 (UTC) | |||
: I don't see your problem here. Relativity says that sizes, masses, rate of passage of time and a bunch of other things depend on the frame of reference of the observer. In your example, people approaching the earth from different directions and speeds would indeed see the earth as having different sizes and shapes simultaneously. The idea that two people perceive things differently because they are moving at different speeds and directions should come as no surprise to you. | |||
: It's not quite a correct analogy - but consider the doppler effect for sound. | |||
: There is a person driving a fast car along a straight road and a person standing still at the side of the road. As he's driving along, the first guy leans on the horn and hears a sound of constant pitch as he passes the guy who's standing still. But the guy standing on the side of the road hears a higher pitched sound as the car approaches him and a lower pitched sound as it passes him and heads off into the distance. Ask the two people what pitch the horn had and they'll disagree. The horn doesn't have to have two pitches simultaneously - it's just that the frame of reference for the two observers is different. Position 100 people at different points along the road, all moving at different speeds and you'll get 100 different perceptions of the exact pitch of the car horn. | |||
:CAVEAT: This isn't actually a very good analogy because sound exhibits doppler differently from the way light does - but the point is that it's OK that an object can simultaneously be perceived as being many different sizes, masses, etc by different observers. | |||
:As I said before, you have to read (and completely understand) things like the ]. In that example, a fast-moving 20' ladder fits into a 10' building - from the point of view of an observer standing next to the building - and the 20' ladder moves through the 5' building from the point of view of an observer riding on the ladder. This is entirely non-contradictory - but it is confusing as all hell for people who aren't comfortable with special relativity. | |||
: So the answer to your first question is that the earth doesn't "morph" - it simply "is" a whole bunch of different sizes (etc) depending on the frame of reference of the observer. | |||
: Your description of what happens with Muons is correct. From our point of view, they are moving ungodly fast, so time for them has slowed down - so they make it through the atmosphere without decaying. From the muons' point of view, time is ticking along normally - but the earth (and it's atmosphere) has contracted to a nearly flat circle and the atmosphere is so thin that it can make it through easily. This is not contradictory - it's an entirely consistent story - and the outcome (that the muon makes it through the atmosphere) is perfectly correct from both viewpoints. | |||
: You boldly assert that "''Different observations can not change physical objects or distances.''" - but you are quite wrong. That is '''exactly''' what does happen. Consider the behavior of muons to be proof of that. There have been numerous other experiments that demonstrate this kind of thing. Special relativity is a proven fact - weird though it seems. You really can fit a 20' ladder into a 10' building if you move it fast enough...but if you're sitting on the ladder, things seem VERY different. | |||
: But think back to my (technically, rather bad) car horn analogy. Different observations of the car horn did change the frequency at which the various observers heard the sound. This is just like that (although the analogy is only perfect for lightwaves - not sound). | |||
: ] (]) 21:17, 31 October 2013 (UTC) | |||
::If I might indulge in a bit of devil's advocacy - the statement "different observations cannot change physical objects" is correct (in this context, although we might get to the Copenhagen Interpretation soon). Different observations change the values of ''measured'' times and distances for a given (unchanging) physical object. The ''object'' doesn't change, although its ''length'' does. ] (]) 21:23, 31 October 2013 (UTC) | |||
:::Yes...we should perhaps think of the "rest length" of an object (like it's "rest mass") as being a constant that doesn't change, and that all practical measurements of the object are a combination of the rest-length and a scaling factor that depends on relative motion. Splitting the length into those two parts resolves the confusion. The object's rest-length is an unchanging property of the object itself but it's modified by a factor that is observer-dependent. However, the key point here is that this second factor isn't like an optical illusion or seeing something in a distorted mirror. The point of the ] is that a fast-moving object doesn't just ''look'' smaller - it will actually fit into a smaller space...from the perspective of some observers. | |||
::: ] (]) 21:46, 31 October 2013 (UTC) | |||
:Your "challenge" is like saying that the rules of ] require objects to grow and shrink. The only difference between that case and this one is that there aren't a bunch of dumb popular books telling you that perspective means that the size of objects is "relative to the observer" and that that has profound philosophical implications. Ignore the second-rate philosophy and you'll be fine -- ] (]) 21:39, 31 October 2013 (UTC) | |||
:: I like that analogy...but we have to be a little careful though. The moon seems like it would fit into a matchbox because of perspective - but we know that it's not "really" that small and that it won't fit into such a small space. With Special Relativity, if the moon were moving so fast that it appeared to be that small, it really '''would''' fit into a matchbox. ] (]) 21:49, 31 October 2013 (UTC) | |||
::: Well, no, for a couple of reasons. First of all, length contraction is only in the direction of motion, so you'd need a Moon-sized matchbox in the other two directions. Then, yes, in the matchbox's frame of reference, you could (very briefly!) have the Moon contained within the top and bottom of the matchbox, say a centimeter apart, but only because you don't agree with the Moon about simultaneity. You'd have to let the Moon in, close the box (that might involve moving the top faster than the speed of light, but whatevs), then bask in the satisfaction that the Moon is inside the box before it obliterates the other side. From the point of view of a lunar observer, the events happen in a different order. --] (]) 21:55, 31 October 2013 (UTC) | |||
== SSRI/SSNRI WITHDRAWAL == | |||
Can someone please add SAVELLA (Milnacipran) withdrawals in with the other SSRI/SSNRI Withdrawal symptoms? It is a fairly new medication, though it has severe withdrawal symptoms, very similar to others you have listed on the page. I would just like others to be informed about coming off this medication. | |||
Thank you kindly, | |||
Laurie Hart <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 19:17, 31 October 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot--> | |||
: If you have a ] that supports the change, then ] and add it, or make a suggestion on the article's talk page. ] (]) 20:27, 31 October 2013 (UTC) | |||
== Effect of poor Eyesight on life skill development == | |||
Can poor eyesight through childhood and adolescence cause any significant lack of life skill development, knowledge etc? ] (]) 22:25, 31 October 2013 (UTC) |
Latest revision as of 08:01, 25 December 2024
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December 13
What is the most iconic tornado photo
Request for opinions |
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The following discussion has been closed. Please do not modify it. |
What photo of a tornado would you say is the most iconic? I'm researching the history of tornado photography for an eventual article on it and I've seen several specific tornadoes pop up over and over again, particularly the Elie, Manitoba F5 and the "dead man walking" shot of the Jarrel, Texas F5. Which would be considered more iconic? ApteryxRainWing🐉 | Roar with me!!! | My contributions 17:21, 13 December 2024 (UTC)
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December 15
help to identify File:Possible Polygala myrtifolia in New South Wales Australia.jpg
Did I get species right? Thanks. Gryllida (talk, e-mail) 06:56, 15 December 2024 (UTC)
- related: https://species.wikimedia.org/Wikispecies:Village_Pump#help_to_identify_species Gryllida (talk, e-mail) 06:57, 15 December 2024 (UTC)
- FWIW, I can't detect any visible differences between the plant in this photo and the ones illustrated in the species and the genus articles. However, the latter makes it clear that Polygala is a large genus, and is cultivated, with hybrids, so it's possible that this one could be a close relative that differs in ways not visible here, such as in the bark or roots. That may or may not matter for your purposes. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 10:11, 15 December 2024 (UTC)
How to address changes to taxonomy
Hi all,
I am a biology student brand new to wiki editing who is interested in cleaning up small articles/stubs for less known taxa. One that I've encountered is a mushroom that occurs in the pacific northwest (Fomitopsis ochracea). The article mentions that this fungus is occasionally mistaken for another fungus, Fomitopsis pinicola.
However, the issue I've run into is that F. pinicola used to be considered a single species found around the world, but relatively recently was split into a few different species. The original name was given to the one that occurs in Europe, and the one in the pacific northwest (and thus could be mistaken for F. ochracea) was given the name Fomitopsis mounceae.
The wiki page says
Historically, this fungus has been misidentified as F. pinicola. When both species are immature, they can look very similar, but can be distinguished by lighting a match next to the surface of the fungus. F. pinicola will boil and melt in heat, while F. ochracea will not.
Since the source says pinicola (as likely do most/all other sources of this info given the change was so recent), and since technically it's true that they used to be mistaken for it... what would be the most appropriate way to modernize that section?
My questions are:
Should I replace F. pinicola with F. mounceae? Or is that wrong because the source doesn't refer to it by that name? Would it be better to write something like (now known as/considered F. mounceae) next to the first mention of the species? Or is that a poor choice because it implies all the members of F. pinicola were renamed F. mounceae?
Any advice on how to go about updating this section is incredibly appreciated
TheCoccomycesGang (talk) 10:21, 15 December 2024 (UTC)
- First, take these sorts of questions to the relevant Wikiproject, in this case Misplaced Pages talk:WikiProject Fungi. I am not as familiar with the consensus at WP:FUNGI, but it seems like they defer to Species Fungorium/Index Fungorium and Mycobank to decide. Those sources presently seem to consider Fomitopsis pinicola a good species. Also, be careful about "replacing", there are rules to ensure the continuity of the article history. By the way, there is a hilarious but unencyclopedic/copyvio recipe appended to the Fomitopsis mounceae article. Abductive (reasoning) 11:09, 15 December 2024 (UTC)
- Thanks for the tips, I didn't know about projects so I'll go read up on that. And thanks for the warnings about replacing things. I've been reading a lot of help pages, but I'm still in the process of learning the all conventions and what mechanics break if you do things the wrong way.
- I actually saw the recipe ages ago before I made my account and completely forgot about it... it was one of many things that prompted me to get into wiki editing. TheCoccomycesGang (talk) 23:12, 15 December 2024 (UTC)
- First, take these sorts of questions to the relevant Wikiproject, in this case Misplaced Pages talk:WikiProject Fungi. I am not as familiar with the consensus at WP:FUNGI, but it seems like they defer to Species Fungorium/Index Fungorium and Mycobank to decide. Those sources presently seem to consider Fomitopsis pinicola a good species. Also, be careful about "replacing", there are rules to ensure the continuity of the article history. By the way, there is a hilarious but unencyclopedic/copyvio recipe appended to the Fomitopsis mounceae article. Abductive (reasoning) 11:09, 15 December 2024 (UTC)
Does stopping masturbation lead to sperm DNA damage?
I'm looking for information on the potential link between the frequency of ejaculation (specifically through masturbation) and sperm DNA damage. I've come across some conflicting information and would appreciate it if someone could point me towards reliable scientific studies or reviews that address this topic.
Specifically, I'm interested in whether prolonged periods of abstinence from ejaculation might have any negative effects on sperm DNA integrity. Any insights or links to relevant research would be greatly appreciated. HarryOrange (talk) 17:08, 15 December 2024 (UTC)
- Only males may abstain from sperm-releasing Masturbation that serves to flush the genital tract of old sperm that in any case will eventually dissipate. No causal relationship between masturbation and any form of mental or physical disorder has been found but abstinence may be thought or taught to increase the chance of wanted conception during subsequent intercourse. Philvoids (talk) 00:51, 16 December 2024 (UTC)
- There's many rumors about that topic. One is that not ejaculating frequently increases the risk of developing prostate cancer. Abductive (reasoning) 01:02, 16 December 2024 (UTC)
- Nothing really conclusive but there's some evidence that short periods are associated with lower DNA fragmentation, see
- Du, Chengchao; Li, Yi; Yin, Chongyang; Luo, Xuefeng; Pan, Xiangcheng (10 January 2024). "Association of abstinence time with semen quality and fertility outcomes: a systematic review and dose–response meta‐analysis". Andrology. 12 (6): 1224–1235. doi:10.1111/andr.13583. ISSN 2047-2919.
- Hanson, Brent M.; Aston, Kenneth I.; Jenkins, Tim G.; Carrell, Douglas T.; Hotaling, James M. (16 November 2017). "The impact of ejaculatory abstinence on semen analysis parameters: a systematic review". Journal of Assisted Reproduction and Genetics. 35 (2): 213. doi:10.1007/s10815-017-1086-0. ISSN 2047-2919. PMC 5845044. PMID 29143943.
- Ayad, Bashir M.; Horst, Gerhard Van der; Plessis, Stefan S. Du; Carrell, Douglas T.; Hotaling, James M. (14 October 2017). "Revisiting The Relationship between The Ejaculatory Abstinence Period and Semen Characteristics". International Journal of Fertility & Sterility. 11 (4): 238. doi:10.22074/ijfs.2018.5192. ISSN 2047-2919. PMC 5641453. PMID 29043697.
- for example. Alpha3031 (t • c) 02:12, 16 December 2024 (UTC)
- Mature sperm cells do not have DNA repair capability. Inevitably, as sperm cells get older, they will naturally and unavoidably be subject to more and more DNA damage. Obviously, freshly produced spermatozoa will, on average, have less DNA damage. It is reasonable to assume that the expected amount of damage is proportional to the age of the cells, which is consistent with what studies appear to find. Also, obviously, the more the damage is to a spermatozoon fertilizing an oocyte, the larger the likelihood that the DNA repair in the resulting zygote, which does have DNA repair capability, will be incomplete. The studies I've looked at did not allow me to assess how much this is of practical significance. --Lambiam 09:40, 16 December 2024 (UTC)
December 16
Abelian sandpile model
Thanks to those who answered my last question, I think it should be added to a disambiguation page. If anyone wants to help me write that, reach out.
A sandpile seems disorganized and inert, but these are critically self-organizing. Do the frequency and size of disturbances on sand dunes and snowy peaks follow power law distribution? Gongula Spring (talk) 01:18, 16 December 2024 (UTC)
- Shouldn't this be at the Math Desk? Abductive (reasoning) 05:12, 16 December 2024 (UTC)
- If the question is not about the model mentioned in the heading but about the physical properties of sand dunes and snowy peaks, this here is the right section of the Reference desk. --Lambiam 08:51, 16 December 2024 (UTC)
- I await a non-mathematical answer. Abductive (reasoning) 09:23, 16 December 2024 (UTC)
- It depends is probably a fairly reasonable non-mathematical answer for these kinds of systems. For sand dunes anyway, sometimes avalanche frequency is irregular and the size distribution follows a power law, and sometimes it's close to periodic and the avalanches span the whole system. It seems there are multiple regimes, and these kinds of systems switch between them. Sean.hoyland (talk) 09:35, 16 December 2024 (UTC)
- Thank you! I'm impressed this seems so casual, but surely you read this somewhere that might have a URL?
- Gongula Spring (talk) 22:29, 19 December 2024 (UTC)
- It depends is probably a fairly reasonable non-mathematical answer for these kinds of systems. For sand dunes anyway, sometimes avalanche frequency is irregular and the size distribution follows a power law, and sometimes it's close to periodic and the avalanches span the whole system. It seems there are multiple regimes, and these kinds of systems switch between them. Sean.hoyland (talk) 09:35, 16 December 2024 (UTC)
- I await a non-mathematical answer. Abductive (reasoning) 09:23, 16 December 2024 (UTC)
- If the question is not about the model mentioned in the heading but about the physical properties of sand dunes and snowy peaks, this here is the right section of the Reference desk. --Lambiam 08:51, 16 December 2024 (UTC)
- Hi, this is an interesting and somewhat open question! A lot of work is done on these models but much less on careful analyses of real dunes. I did find this dissertation that is freely accessible and describes some physical experiments and how well they fit various models. The general answer seems to be that the power law models are highly idealized, and determining the degree to which any real system's behavior is predicted by the model ahead of time is very difficult. Update: This is one of the earlier important works on the topic and it does include discussion of how well the model fits experiments.SemanticMantis (talk) 17:21, 16 December 2024 (UTC)
- That dissertation is great!
- Gongula Spring (talk) 22:30, 19 December 2024 (UTC)
Polar night
Are there any common or scientific names for types of polar night? The types that I use are:
- polar night - meaning a day when sun's altitude remains below horizon entire day (there is no daylight at solar noon, only civil twilight), occurring poleward from 67°24′ north or south
- civil polar night - meaning a day when sun's altitude remains below -6° entire day (there is no civil twilight at solar noon, only nautical twilight), occurring poleward from 72°34′ north or south
- nautical polar night - meaning a day when sun's altitude remains below -12° entire day (there is no nautical twilight at solar noon, only astronomical twilight), occurring poleward from 78°34′ north or south
- astronomical polar night - meaning a day when sun's altitude remains below -18° entire day (there is no astronomical twilight at solar noon, only night), occurring poleward from 84°34′ north or south
These names were changed on Polar night article, and I wnat to know whether these named I listed are in use in any scientific papers, or in common language. (And I posted that question here and not in language desk because I think that this is not related to language very tightly.) --40bus (talk) 18:56, 16 December 2024 (UTC)
- Some definitions at The Polar Night (1996) from the Aurora Research Institute. Alansplodge (talk) 22:55, 16 December 2024 (UTC)
- These seem to be generalizable as: X polar night is a period, lasting not less than 24 hours, during which the sun remains below the horizon and there is no X twilight. The specific definitions depend then on the specific definitions of civil/nautical/astronomical twilight. These can be defined with a subjective observational standard or with an (originally experimentally determined) objective standard. --Lambiam 10:36, 17 December 2024 (UTC)
- FWIW, I as a former amateur astronomer have never previously thought about the question of Polar twilight and night nomenclatures, but immediately and completely understood what the (previously unencountered) terms used in the query must mean without having to read the attached descriptions. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 16:34, 17 December 2024 (UTC)
- These seem to be generalizable as: X polar night is a period, lasting not less than 24 hours, during which the sun remains below the horizon and there is no X twilight. The specific definitions depend then on the specific definitions of civil/nautical/astronomical twilight. These can be defined with a subjective observational standard or with an (originally experimentally determined) objective standard. --Lambiam 10:36, 17 December 2024 (UTC)
December 17
differential equations with complex coefficients
In an intro ODE class one basically studies the equation where x is a real vector and A is a real matrix. A typically has complex eigenvalues, giving a periodic or oscillating solution to the equation. That is very important in physics, which has various sorts of harmonic oscillators everywhere. If A and x are complex instead of real, mathematically the ODE theory works out about the same way. I don't know what happens with PDE's since I haven't really studied them.
My question is whether the complex case is important in physics the way the real case is. Can one arrive at it through straightforward coordinate transformations? Do the complex eigenvalues "output" from one equation find their way into the "input" of some other equation? Does the distance metric matter? I.e. in math and old-fashioned physics we use the Euclidean metric, but in realtivity one uses the Minkowski metric, so I'm wondering if that leads to complex numbers. This is all motivated partly by wondering where all the complex numbers in quantum mechanics come from. Thanks. 2601:644:8581:75B0:0:0:0:DA2D (talk) 22:54, 17 December 2024 (UTC)
- Perhaps I don't understand what you are getting at but simple harmonic motion is xdot=j*w*x where w is angular frequency and j is i Greglocock (talk) 00:35, 18 December 2024 (UTC)
- If PDEs count, the Schrödinger equation and the Dirac equation are examples of differential equations in the complex domain. A linear differential equation of the form on the complex vector space can be turned into one on the real vector space . For a very simple example, using the equation can be replaced by
- --Lambiam 01:11, 18 December 2024 (UTC)
- Shouldn't this be at the Math Desk? It almost seems like the IP could be trolling, given the same question just above. Abductive (reasoning) 14:49, 18 December 2024 (UTC)
- The question whether the complex case is important in physics the way the real case is, is not a maths issue. IMO the Science section is the best choice. I do not see another post that asks the same or even a related question. --Lambiam 21:51, 18 December 2024 (UTC)
- Just as above, I await a non-mathematical answer to this question. Abductive (reasoning) 07:01, 19 December 2024 (UTC)
- The question whether the complex case is important in physics the way the real case is, is not a maths issue. IMO the Science section is the best choice. I do not see another post that asks the same or even a related question. --Lambiam 21:51, 18 December 2024 (UTC)
- Shouldn't this be at the Math Desk? It almost seems like the IP could be trolling, given the same question just above. Abductive (reasoning) 14:49, 18 December 2024 (UTC)
Thanks all. Greglocock, your SHO example is 1-dimensional but of course you can have a periodic oscillator (such as a planetary orbit) in any orientation in space, you can have damped or forced harmonic oscillators, etc. Those are all described by the same matrix equation. The periodic case means that the matrix eigenvalues are purely imaginary. The damped and forced cases are where there is a real part that is negative or positive respectively. Abductive, of course plenty of science questions (say about how to calculate an electron's trajectory using Maxwell's equations) will have mathematical answers, and the science desk is clearly still the right place for them, as they are things you would study in science class rather than math class. Lambiam, thanks, yes, PDE's are fine, and of course quantum mechanics uses complex PDE's. What I was hoping to see was a situation where you start out with real-valued DEs in some complicated system, and then through some coupling or something, you end up with complex-valued DEs due to real matrices having complex eigenvalues. Also I think the Minkowski metric can be treated like the Euclidean one where the time coordinate is imaginary. But I don't know how this really works, and Misplaced Pages's articles about such topics always make me first want to go learn more math (Lie algebras in this case). Maybe someday. 2601:644:8581:75B0:0:0:0:DA2D (talk) 07:25, 19 December 2024 (UTC)
December 18
Why don't all mast radiators have top hats?
Our mast radiator article describes a device called a "top hat" which increases the range for mast radiators that can't be built tall enough.
So, why would you bother building a mast radiator without a top hat? Couldn't you just build it shorter with the top hat, and save steel? Marnanel (talk) 15:00, 18 December 2024 (UTC)
- The main source cited in our article states, "
Top loading is less desirable than increased tower height but is useful where towers must be electrically short due to either extremely low carrier frequencies or to aeronautical limitations. Top loading increases the base resistance and lowers the capacitive base reactance, thus reducing the Q and improving the bandwidth of towers less than 90° high.
" If "reducing the Q" is an undesirable effect, this is a trade-off design issue in which height seems to be favoured if circumstances permit. --Lambiam 21:41, 18 December 2024 (UTC)
Name of our solar system
Is our star system officially called "Sol", or is that just something that came from science fiction and then became ubiquitous? 146.90.140.99 (talk) 22:06, 18 December 2024 (UTC)
- It's called the Solar System, and its star is called Sol, from Latin via French. Hence terms like "solstice", which means "sun stands still" in its apparent annual "sine wave" shaped path through the sky. ←Baseball Bugs carrots→ 23:31, 18 December 2024 (UTC)
- Via French? According to the OED, it came direct from Latin. --Lambiam 11:45, 19 December 2024 (UTC)}}
- Old French plus Latin. ←Baseball Bugs carrots→ 14:25, 19 December 2024 (UTC)
- Also in Old French, the word meaning "sun" was soleil. --Lambiam 23:42, 19 December 2024 (UTC)
- Old French plus Latin. ←Baseball Bugs carrots→ 14:25, 19 December 2024 (UTC)
- Via French? According to the OED, it came direct from Latin. --Lambiam 11:45, 19 December 2024 (UTC)}}
- Let's say to that claim. The star is indeed called Sol if you're speaking Latin, but in English it's the Sun (or sun). Of course words like "solar" and "solstice" derive from the Latin name, but using "Sol" to mean "the Sun" does seem to be something from science fiction. --142.112.149.206 (talk) 06:04, 19 December 2024 (UTC)
- "Sol" is occasionally used to mean the Sun by astronomers. I feel like it is used in contexts where it is necessary to distinguish our experience with the Sun here on Earth, such as sunsets, from more "sterile" aspects of the Sun one might experience off the Earth. Abductive (reasoning) 08:56, 19 December 2024 (UTC)
- Being an astronomer myself, I don't think I've ever heard anyone use "Sol" outside of a science fiction context. --Wrongfilter (talk) 09:06, 19 December 2024 (UTC)
- Scientific articles that use the term Sol; Development of the HeliosX mission analysis code for advanced ICF space propulsion and Swarming Proxima Centauri: Optical Communication Over Interstellar Distances. These are rather speculative but as I mentioned, the usage is for off-planet situations. Abductive (reasoning) 13:05, 19 December 2024 (UTC)
- Using Sol, Terra and Luna to refer to the Sun, Earth and Moon only happens if you write your entire article in Latin and in science fiction, not in regular science articles. They are capitalised though. Just as people write about a galaxy (one of many) or the Galaxy (the Milky Way Galaxy, that's our galaxy). The Solar System is also capitalised. PiusImpavidus (talk) 10:38, 19 December 2024 (UTC)
- The article says "Sol" is the "personification" of the sun. Google Image the term "old Sol" and you'll see plenty of images of the sun with a face, not just Sci-Fi stuff. And "Luna" is obviously the basis for a number of words not connected with Sci-Fi. Lunar orbit, lunar module, etc. And the term "terra firma" has often been used in everyday usage. ←Baseball Bugs carrots→ 11:34, 19 December 2024 (UTC)
- And yet, if you ask 1,000 people "What's that big yellow thing up in the sky called?", you'll get 1,000 "the Sun"s and zero "Sol"s. Yes, in specialised contexts, Sol is used; but that doesn't justify saying our solar system's star "is called Sol" without any qualification, as if that were the normal, default term. It's not. -- Jack of Oz 12:16, 19 December 2024 (UTC)
- And after you've gotten that response, ask them why it isn't the "Sunner System". And why a sun room attached to a house isn't called a "sunarium". And why those energy-gathering plates on some roofs are not called "sunner panels". ←Baseball Bugs carrots→ 14:22, 19 December 2024 (UTC)
- What does that have to do with anything? The question was 'Is our star system officially called "Sol"?' (my emphasis). The answer is it is not. And that does not preclude other terms being derived from Latin sol (or, often enough, from Greek helios), nobody denies that, it is irrelevant to the question. --Wrongfilter (talk) 14:52, 19 December 2024 (UTC)
- The problem is that the OP's question contains false premises. One is the question of what the "official" name is. There is no "official" name. It's the "conventional" name. And the second part, claiming that "Sol" comes from Sci-fi, is demonstrably false. ←Baseball Bugs carrots→ 15:05, 19 December 2024 (UTC)
- Then demonstrate (that the usage of "Sol" as a name for the Sun, in English, not its use to derive adjectives, originated outside of SF), with references. The original question does not even include any premises, with maybe the exception of "ubiquitous". --Wrongfilter (talk) 15:18, 19 December 2024 (UTC)
- "Is our star system officially called "Sol" , or is that just something that came from science fiction and then became ubiquitous? ". And the wording of your own question, just above, does not make sense. ←Baseball Bugs carrots→ 15:24, 19 December 2024 (UTC)
- Looking at Newspapers.com (pay site), I'm seeing colloquial references to "old Sol" (meaning the sun) as far back as the 1820s. No hint of sci-fi derivation. ←Baseball Bugs carrots→ 15:32, 19 December 2024 (UTC)
- Great! Well done. --Wrongfilter (talk) 15:41, 19 December 2024 (UTC)
- Feel free to box up this section. ←Baseball Bugs carrots→ 15:52, 19 December 2024 (UTC)
- Great! Well done. --Wrongfilter (talk) 15:41, 19 December 2024 (UTC)
- Looking at Newspapers.com (pay site), I'm seeing colloquial references to "old Sol" (meaning the sun) as far back as the 1820s. No hint of sci-fi derivation. ←Baseball Bugs carrots→ 15:32, 19 December 2024 (UTC)
- The 1933 OED entry for Sol, linked to above, gives several pre-SF uses, the earliest from 1450. --Lambiam 23:48, 19 December 2024 (UTC)
- Yes, of course, but that's not surprising, is it? 15th century humanists, astrologers and pre-Victorian poets liked to sprinkle their texts with Latin words. But I don't think this is what the question is about. It's a matter of context, but it should be up to OP to clarify that. --Wrongfilter (talk) 08:48, 20 December 2024 (UTC)
- It's not surprising, but the discussion was not whether the use of Sol in English texts is surprising, but whether it originated outside of SF. --Lambiam 10:52, 20 December 2024 (UTC)
- In my view, the question has a clear scifi bent, and that particular usage ("Where shall we go for our vacation? Alpha Centauri or Sol?") does not originate in the 15th century. The word is much older, of course it is, but the usage is not. In the 15th century people didn't even know that the Sun is just an ordinary star and could do with a particular name to distinguish it from the others. The connotations of sol were vastly different from what they are today and from what is implied in OP's question. Incidentally, the IAU doesn't even define a name , although they recommend using capitalised "Sun". Certainly no "Sol" anywhere. --Wrongfilter (talk) 12:04, 20 December 2024 (UTC)
- It's not surprising, but the discussion was not whether the use of Sol in English texts is surprising, but whether it originated outside of SF. --Lambiam 10:52, 20 December 2024 (UTC)
- Yes, of course, but that's not surprising, is it? 15th century humanists, astrologers and pre-Victorian poets liked to sprinkle their texts with Latin words. But I don't think this is what the question is about. It's a matter of context, but it should be up to OP to clarify that. --Wrongfilter (talk) 08:48, 20 December 2024 (UTC)
- "Is our star system officially called "Sol" , or is that just something that came from science fiction and then became ubiquitous? ". And the wording of your own question, just above, does not make sense. ←Baseball Bugs carrots→ 15:24, 19 December 2024 (UTC)
- Then demonstrate (that the usage of "Sol" as a name for the Sun, in English, not its use to derive adjectives, originated outside of SF), with references. The original question does not even include any premises, with maybe the exception of "ubiquitous". --Wrongfilter (talk) 15:18, 19 December 2024 (UTC)
- The problem is that the OP's question contains false premises. One is the question of what the "official" name is. There is no "official" name. It's the "conventional" name. And the second part, claiming that "Sol" comes from Sci-fi, is demonstrably false. ←Baseball Bugs carrots→ 15:05, 19 December 2024 (UTC)
- What does that have to do with anything? The question was 'Is our star system officially called "Sol"?' (my emphasis). The answer is it is not. And that does not preclude other terms being derived from Latin sol (or, often enough, from Greek helios), nobody denies that, it is irrelevant to the question. --Wrongfilter (talk) 14:52, 19 December 2024 (UTC)
- And after you've gotten that response, ask them why it isn't the "Sunner System". And why a sun room attached to a house isn't called a "sunarium". And why those energy-gathering plates on some roofs are not called "sunner panels". ←Baseball Bugs carrots→ 14:22, 19 December 2024 (UTC)
- Does that make it a Sol-ecism? Clarityfiend (talk) 12:19, 19 December 2024 (UTC)
- More like a Sol-ips-ism. Meaning a factory where suns are made. From Sol = sun, and ipso = facto. Thus endeth the entymogology lesson for today. Go in peace to love and serve whomsoever. -- Jack of Oz 19:37, 19 December 2024 (UTC)
- And yet, if you ask 1,000 people "What's that big yellow thing up in the sky called?", you'll get 1,000 "the Sun"s and zero "Sol"s. Yes, in specialised contexts, Sol is used; but that doesn't justify saying our solar system's star "is called Sol" without any qualification, as if that were the normal, default term. It's not. -- Jack of Oz 12:16, 19 December 2024 (UTC)
- The article says "Sol" is the "personification" of the sun. Google Image the term "old Sol" and you'll see plenty of images of the sun with a face, not just Sci-Fi stuff. And "Luna" is obviously the basis for a number of words not connected with Sci-Fi. Lunar orbit, lunar module, etc. And the term "terra firma" has often been used in everyday usage. ←Baseball Bugs carrots→ 11:34, 19 December 2024 (UTC)
- Being an astronomer myself, I don't think I've ever heard anyone use "Sol" outside of a science fiction context. --Wrongfilter (talk) 09:06, 19 December 2024 (UTC)
- "Sol" is occasionally used to mean the Sun by astronomers. I feel like it is used in contexts where it is necessary to distinguish our experience with the Sun here on Earth, such as sunsets, from more "sterile" aspects of the Sun one might experience off the Earth. Abductive (reasoning) 08:56, 19 December 2024 (UTC)
Mountains
Why there are no mountains on Earth with a height above 10,000 m? As the death zone is about at 8,000 m, and above 19,000 m, there is an Armstrong limit, where water boils at normal human body temperature, it is good that there are no more mountains higher than 8,000 km than just 14, but if there were hundreds of mountains above 9,000 m, then these were bad to climb. If there were different limits for death zone and Armstrong limit, would then there be possible to have higher mountains? I have just thought that, it is not a homework? --40bus (talk) 22:29, 18 December 2024 (UTC)
- There are mountains elsewhere in the solar system that are over 20km high. Given that some of those are on airless worlds, I don't think the air pressure has any bearing on it. 146.90.140.99 (talk) 22:57, 18 December 2024 (UTC)
- Multiple sources from web searching suggest the theoretical maximum height for mountains on Earth is around 15,000 m – the limiting factor is Isostasy; the higher (therefore more voluminous) a mountain is, the more its weight causes the crust beneath it to sink. The actual heights of mountains are a trade-off between how fast tectonic movements can raise them versus isostatic sinking and how quickly they are eroded, and tectonic movements do not last for ever. See also Orogeny. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 00:25, 19 December 2024 (UTC)
- And erosion goes faster as the mountain gets higher, in particular when it's high enough to support glaciers – one reason why mountains can get higher on an airless world. Now it gets interesting for a mountain high enough to reach into the stratosphere, as it would be too dry to have anything but bare rock. I suppose it would locally raise the tropopause, preventing that. PiusImpavidus (talk) 11:13, 19 December 2024 (UTC)
December 19
Does human DNA become weaker with each generation?
As with photocopying something over and over, the text becomes less clear each time.
Does human DNA become weaker with each generation? HarryOrange (talk) 21:22, 19 December 2024 (UTC)
- Sure, DNA replication is not perfect, although proofreading reduces the error rate to about 1 mistake per 10 nucleotides (see our article on DNA Replication). But that is per generation of cells, not of the whole organisms. Many mutations will be neutral in effect (because much of our DNA is redundant), some will be deleterious, and a few might be advantageous. It is the process of natural selection that hinders the spread of deleterious mutations: sometimes this aspect is called purifying selection. One thus usually expects a stable mutation–selection balance over time rather than that "DNA becomes weaker with each generation". Medical science is reducing the selection pressure against some mutations, which consequently may become more common. One of the problems for asexual organisms is referred to as Muller's ratchet; assuming that reverse mutations are rare, each generation has at least the mutational load of its predecessor. In contrast, in sexual organisms genetic recombination generates the variation that, combined with selection, can repair the situation. Sexual organisms consequently have a lighter genetic load. JMCHutchinson (talk) 22:42, 19 December 2024 (UTC)
- So purifying selection won't work properly in case of Inbreeding ? HarryOrange (talk) 23:16, 19 December 2024 (UTC)
- The larger the degree of inbreeding, the larger the chance that deleterious traits are expressed. But this very expression of traits leading to decreased biological fitness of their bearers is what actually enables purifying selection in the longer term. --Lambiam 23:36, 19 December 2024 (UTC)
- @Lambiam so DNA repair won't stop these deleterious traits to get expressed? HarryOrange (talk) 14:11, 20 December 2024 (UTC)
- No, this is not an issue of damage to the DNA. The genes involved are faithfully reproduced and passed on from generation to generation. --Lambiam 15:53, 20 December 2024 (UTC)
- @Lambiam so DNA repair won't stop these deleterious traits to get expressed? HarryOrange (talk) 14:11, 20 December 2024 (UTC)
- The larger the degree of inbreeding, the larger the chance that deleterious traits are expressed. But this very expression of traits leading to decreased biological fitness of their bearers is what actually enables purifying selection in the longer term. --Lambiam 23:36, 19 December 2024 (UTC)
- So purifying selection won't work properly in case of Inbreeding ? HarryOrange (talk) 23:16, 19 December 2024 (UTC)
- Or stronger e.g. "...we found that genes specifically duplicated in the Greenland shark form a functionally connected network enriched for DNA repair function", and those guys live for centuries and have much more DNA than us. Sean.hoyland (talk) 15:21, 20 December 2024 (UTC)
- @Lambiam If not due to DNA damage, why do babies from inbreeding appear like DNA-damaged species? HarryOrange (talk) 17:29, 20 December 2024 (UTC)
- Inbred offspring of species that normally outcross may show abnormalities because they are more likely than outcrossed offspring to be homozygous for recessive alleles that are deleterious. In individuals that are heterozygous at these loci, the recessive alleles will not be expressed (because the other wild-type dominant allele is sufficient to do their job adequately). See our article on inbreeding depression. JMCHutchinson (talk) 19:26, 20 December 2024 (UTC)
- @Lambiam If not due to DNA damage, why do babies from inbreeding appear like DNA-damaged species? HarryOrange (talk) 17:29, 20 December 2024 (UTC)
Larvae going south
In a novel I've just finished (The Chemistry of Death by Simon Beckett) he writes:
- leave the body in an orderly fashion, following each other in a neat procession that always heads south. South-east or south-west sometimes, but never north. No-one knows why.
The author has done considerable international research on the science of forensic identification of decayed bodies and I assume his details can be trusted.
I've looked online for any verification of this surprising statement, but found only this, which seems to debunk it.
Is there any truth to this? -- Jack of Oz 23:38, 19 December 2024 (UTC)
- Can't speak to its truth, but . . .
- Does Beckett state this in his own auctorial voice (i.e. as an omniscient narrator)? If so, he might be genuinely mistaken.
- The book was published nearly 20 years ago, what was the accepted wisdom then?
- What specific species (if any) is the book describing? – your linked Quora discussion refers only to "maggots" (which can be of numerous species and are a kind of larva, but there are many others, including for example Processionary caterpillars).
- Alternatively, if the statement is made by a character in the book, is that character meant to be infallible, or is he portrayed as less than omniscient, or an 'unreliable narrator'?
- Regarding the statement, in the Northern hemisphere the arc of South-east to South-west is predominently where the Sun is found well above the horizon, the North never, so the larvae involved might simply be seeking maximum warmth or light. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 02:18, 20 December 2024 (UTC)
- This appears in the very first paragraph of Chapter I, which starts out:
- A human body starts to decompose four minutes after death. Once the encapsulation of life, it now undergoes its final metamorphoses. It begins to digest itself. Cells dissolve from the inside out. Tissue turns to liquid, then to gas. No longer animate, the body becomes an immovable feast for other organisms. Bacteria first, then insects. Flies. Eggs are laid, then hatched. The larvae feed on the nutrient-rich broth, and then migrate. They leave the body in an orderly fashion ... (then the quote above completes the paragraph).
- It's not until para 2 that he starts talking about any human characters, and not until para 4 that he invokes the first person.
- That's as much as I know. But I find it hard to believe he'd just make up a detail and put it in such a prominent place if it could so easily be debunked if it were not true. -- Jack of Oz 02:39, 20 December 2024 (UTC)
- I wonder how they would measure the migratory path of maggots within a sealed coffin. ←Baseball Bugs carrots→ 02:51, 20 December 2024 (UTC)
- The context of the novel is about finding decaying corpses that have been dumped in a forest. No coffins involved. -- Jack of Oz 06:08, 20 December 2024 (UTC)
- Baseball Bugs, see also body farm research facilities. Alansplodge (talk) 13:44, 20 December 2024 (UTC)
- Could it be that the larvae are setting off in search of another corpse? The prevailing wind in the UK is from the south-west, so by heading into the wind they won't be distracted by the frangrance of the one they've just left. Shantavira| 09:30, 20 December 2024 (UTC)
- The context of the novel is about finding decaying corpses that have been dumped in a forest. No coffins involved. -- Jack of Oz 06:08, 20 December 2024 (UTC)
- I wonder how they would measure the migratory path of maggots within a sealed coffin. ←Baseball Bugs carrots→ 02:51, 20 December 2024 (UTC)
- This appears in the very first paragraph of Chapter I, which starts out:
If you can, have a look at 'Heinrich, Bernd. “Coordinated Mass Movements of Blow Fly Larvae (Diptera: Calliphoridae).” Northeastern Naturalist, vol. 20, no. 4, 2013, pp. N23–27. JSTOR, http://www.jstor.org/stable/43288173.' Here are some extracts
- On the fourth day, after a cooling night with dew on the grass, a stream of tens of thousands of larvae exited from beneath the carcass within 1 h after sunrise, and proceeded in a single 1-2-cm-wide column directly toward the rising sun...
- However, in this case, the larvae left at night, within 1 h after a cloudburst (at 21 :00 hours). But, unlike before, this nocturnal larval exodus in the rain was diffuse; thousands of larvae spread out in virtually all directions over an 8 m2area. Apparently, the sudden moisture had cued and facilitated the mass exodus, but the absence of sun had prevented a unidirectional, en masse movement.
- However, on the following morning as the sun was starting to illuminate the carcass on the dewy grass, masses of larvae gathered at the east end of the carcass at 07:00 hours. In one half hour later, they started streaming in a column directly (within one degree) toward the rising sun, and the carcass was then nearly vacated.
It goes on. Maggot migration appears to be a bit more complicated than the novel suggests. Sean.hoyland (talk) 09:39, 20 December 2024 (UTC) I suppose you could try to address it from the other direction and look at the technology your average maggot has access to in terms of light detection, heat detection, olfactory systems, orientation in magnetic fields (like many arthropods) etc. They presumably have quite a lot of tools. Sean.hoyland (talk) 10:13, 20 December 2024 (UTC)
- If orderly migrating maggots tend to move towards the sun, they should display a northward tendency in Oztralia. --Lambiam 10:31, 20 December 2024 (UTC)
- Maybe, but the novel is set in England.
- I must say, as soon as I read the quoted para for the first time, my immediate thought was that it might have something to do with the magnetic field of the earth. -- Jack of Oz 10:42, 20 December 2024 (UTC)
- Prime suspect might be the Bolwig organ, the photoreceptor cluster many fly larvae have. Sean.hoyland (talk) 10:49, 20 December 2024 (UTC)
- Obviously, Jack, you need to create a corpse, place it in a nearby forest, and carefully observe which way the maggots go. For Science! And Literary Criticism! {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 21:01, 20 December 2024 (UTC)
December 20
Winter solstice and time of sunrise?
How is it that despite December 21st supposedly being the shortest day of the year, sunrise here happens later and later until December 26 and only on January 05 starts to turn around to occur earlier and earlier. On December 25 it takes place at about 08:44, between December 26 and January 04 it takes place at about 08:45, and on January 05 it takes place again at about 08:44. (Google rounds out the seconds). Is it Google's fault? Is it everywhere the same? Confused in Brussels, Belgium. 178.51.16.158 (talk) 12:06, 20 December 2024 (UTC)
- The pertinent article is Analemma, start with the section Earliest and latest sunrise and sunset. The details are not that simple to understand, but it's basically due to the ellipticity of Earth's orbit and its axial tilt. --Wrongfilter (talk) 12:22, 20 December 2024 (UTC)
- Also note that sunset begins to be later on 22 December so that the time between sunrise and sunset is a few seconds longer than on 21 December (3 seconds longer on 22/12/24 in Brussels according to this). Alansplodge (talk) 13:33, 20 December 2024 (UTC)
- Also see Equation of time#Major components. The obliquity of the ecliptic (that is, the Earth's axial tilt) is the main component and hardest to understand. But the idea is that the time when the Sun is exactly south (that is, the true noon) moves some minutes back and forth throughout the year and it moves quite rapidly to later times in late December. PiusImpavidus (talk) 19:05, 20 December 2024 (UTC)
Three unit questions
- Why territorial waters are defined by nautical miles instead of kilometers?
- Why GDP is usually measured in US dollars rather than euros? Euro would be better because it is not tied into any country.
- Are there any laws in United States that are defined by metric units?
--40bus (talk) 23:30, 20 December 2024 (UTC)
- There were nautical miles in use before there were kilometers.
- There were US dollars in use before there were Euros.
- Yes.
- The questions all reduce to Why can't millions of people make a change of historically widely accepted units that continue to serve their purpose, and convert to different units that would have no substantive difference, because someone has an opinion. Philvoids (talk) 00:52, 21 December 2024 (UTC)
- Do any people use metric units in marine and air navigation like "The ship is 10 kilometers from the port", "The plane is 10 kilometers from the destination? And is there any European country with metric flight levels? --40bus (talk) 07:22, 21 December 2024 (UTC)
- Inland shipping (rivers, canals and lakes) in Europe (except the UK) is fully metric. Ships going for example Tilbury – Duisburg may have to switch units along the way. Gliders and ultralight aircraft in Europe often use metric instruments and airport dimensions are also metric (including runway length). Countries are free to define their territorial waters in whatever way they deem fit, so with nautical miles having no legal status in a fully metric country, they may define their territorial waters as extending 22224 metres. PiusImpavidus (talk) 11:23, 21 December 2024 (UTC)
- Our nautical mile article says: "In 1929 the international nautical mile was defined by the First International Extraordinary Hydrographic Conference in Monaco as exactly 1,852 metres (which is 6,076.12 ft). The United States did not adopt the international nautical mile until 1954. Britain adopted it in 1970..."
- Inland shipping (rivers, canals and lakes) in Europe (except the UK) is fully metric. Ships going for example Tilbury – Duisburg may have to switch units along the way. Gliders and ultralight aircraft in Europe often use metric instruments and airport dimensions are also metric (including runway length). Countries are free to define their territorial waters in whatever way they deem fit, so with nautical miles having no legal status in a fully metric country, they may define their territorial waters as extending 22224 metres. PiusImpavidus (talk) 11:23, 21 December 2024 (UTC)
- As the US customary units are actually defined in terms that relate them to metric units, any US law based on measurements is technically defined by metric units.--User:Khajidha (talk) (contributions) 01:55, 21 December 2024 (UTC)
- The US dollar has been the world's dominant reserve currency for about 75 years. As for the metric system in the US, it is standard in scientific, medical, electronics, auto manufacturing and other highly technical industries. By law, all packaged foods and beverages have metric quantities as well as customary quantities. See Metrication in the United States. Cullen328 (talk) 02:28, 21 December 2024 (UTC)
- Do any people use metric units in marine and air navigation like "The ship is 10 kilometers from the port", "The plane is 10 kilometers from the destination? And is there any European country with metric flight levels? --40bus (talk) 07:22, 21 December 2024 (UTC)
The Wikipaedia article on the Nautical Mile talks about how the term originated, it was originally defined in terms of latitude not as a number of meters 114.75.48.128 (talk) 10:03, 24 December 2024 (UTC)
December 24
Unknown species of insect
Am I correct in inferring that this guy is an oriental beetle? I was off-put by the green head at first, but the antennae seem to match. JayCubby 03:00, 24 December 2024 (UTC)
(reference: https://www.genesdigest.com/macro/image.php?imageid=168&apage=0&ipage=1)
It looks like one of the invasive Japanese beetles that happens to like my blackberries in the summer.Modocc (talk) 13:11, 24 December 2024 (UTC)
- I would say not necessarily a Japanese beetle, but almost certainly one of the other Scarab beetles, though with 35,000 species that doesn't help a lot. Looking at the infobox illustration in that article, 16. & 17., "Anisoplia segetum" looks very similar, but evidently we either don't have an article or (if our Anisoplia article is a complete list) it's been renamed. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 14:18, 24 December 2024 (UTC)
- Yes, it's not the Japanese beetle for this beetle appears to lack its white-dotted fringe although its condition is deteriorated. Its shape is also more or less more slender; and not as round. Modocc (talk) 15:02, 24 December 2024 (UTC)
- Perhaps it is the shining leaf chafer Strigoderma pimalis. Shown here. Modocc (talk) 16:09, 24 December 2024 (UTC)
- That looks like easily the best match I've seen so far, and likely correct. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 17:09, 24 December 2024 (UTC)