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October 30

Locomotive efficiency

What is the highest thermal efficiency ever achieved by a steam locomotive? I know their typical efficiency is only 5-10%, yet I've read somewhere that some of them (notably some of the later French De Glenn compounds) achieved an efficiency of up to 25% (at the cost of greatly complicating both operation and maintenance) -- is that true? 2601:646:8E01:7E0B:65AB:303D:F2EB:232 (talk) 06:16, 30 October 2017 (UTC)[reply]

Locomotive engines in particular face severe practical limitations that reduce their efficiency. Even battleships had to make some compromise in their reciprocating steam engines, for example few if any used quad expansion expansion engines. Even so the efficiency of their massive engines maxed out at 13%. Derived from "Ship Form, Resistance and Screw Propulsion" by GS Baker, published in 1920. So how could the necessarily compromised railway locomotives get double that? By going to a steam turbine possibly. But that incurs losses in the transmission. I suggest you challenge the 25% figure, it doesn't pass the sniff test. Greglocock (talk) 06:44, 30 October 2017 (UTC)[reply]

Coincidentally the highest efficiency I can find for a Andre Chapelon design is 12%. Greglocock (talk) 06:55, 30 October 2017 (UTC)[reply]

And 12-13% for Argentina https://static1.squarespace.com/static/55e5ef3fe4b0d3b9ddaa5954/t/55e637bee4b0bef289260255/1441150910433/%23+DOMS-2_PORTA_Argentina.pdf Greglocock (talk) 07:09, 30 October 2017 (UTC)[reply]

The most efficient weren't the French de Glehn's, but rather Chapelon's larger 8-coupled locos, the 242 A 1 and 240P. Another couple of engineers worth looking at L.D. Porta in Argentina and David Wardale's Red Devil in South Africa. Much of this later work wasn't about thermal efficiency so much as improved mechanics (the developing technology of the time was offering useful developments here, such as roller bearings), and in more efficient combustion with worse fuels. Porta's Gas Producer Combustion System in particular. Koopmans. The Fire Burns Much Better. ISBN 1909358053. is an important text in this field.

A steam locomotive is first of all a locomotive: it has to move itself, it has to fit through the railway loading gauge. This has always been a limitation on their performance and the sophistication possible. As a result they always lagged behind marine and stationary engine practice. High boiler pressures, steam turbines, condensing and even superheating either didn't appear on locomotives or only later and with less success. Turbines in particular were a notable failure owing to the lack of a successful high pressure watertube boiler and the only one that was adequately reliable was the Turbomotive, the least technically adventurous of them. Andy Dingley (talk) 11:01, 30 October 2017 (UTC)[reply]

I found a project to rebuild a 1956 locomotive, ATSF 3463, to run on torrified biomass. The modernised boiler arrangement is being claimed to double the original thermal efficiency, although there is much scepticism [1]. Alansplodge (talk) 17:16, 30 October 2017 (UTC)[reply]

Whatever the peak efficiency was, it was likely "topped" by the DR 18 201. Unfortunately for you it was not common in the steam engine technology to measure efficiency in "%". Never the less i doubt classical steam engines can manage more than 10%, because they only use the pressure part of the total thermal energy and even that rather unefficient. Steam turbine systems in power stations can reach up to 45% but these are huge, stationary cyclic systems with buid investments of up to 1 billion $, so its sure that these are all state of the art in peak efficient at the time they where build. --Kharon (talk) 01:30, 31 October 2017 (UTC)[reply]

A rather out-of-sequence one-off loco, not particularly fast (182.4 km/h or 113.3 mph is not exceptional for steam locos) and designed in its day just to be fast enough to test new coaching stock (see the MÁV Class 242 too). It's notable today for having been preserved, not for its speed. There's no indication that it was ever especially efficient. Andy Dingley (talk) 11:28, 31 October 2017 (UTC)[reply]

"they only use the pressure part of the total thermal energy" Also you're wrong there too. There wasn't a huge amount of attention paid to this, but some designers (notably Chapelon and Stumpf with his uniflow designs) did do so. Andy Dingley (talk) 00:17, 2 November 2017 (UTC)[reply]

[un-indent] Thanks, all! No wonder diesels replaced steam trains so quickly... 2601:646:8E01:7E0B:B9F4:7CD7:EC0A:69F7 (talk) 04:18, 3 November 2017 (UTC)[reply]

Mostly that wasn't the reason. Energy was cheap, so it wasn't a major driving factor. However after WWI, staff costs became very expensive, so they were the main driver. It costs two people on the footplate of a steam engine (affordable) but also a lot more of them in the engine shed and mostly, the cost of the two footplate crew have to be paid over a long, long working day even when the loco only does useful billable work for a small part of this. They have to be lit up and warmed through long before they're ready, then cleaned and oiled (usually by junior staff). At the end of the day there's another hour or two's work to put the engine away. If the service is to take a train down Thomas' branchline and wait for the afternoon return train at the far end, that's still time when the fireman has to look after a hot engine in steam (and burning a small quantity of fuel). Then the loco takes a day off once a fortnight or month for a boiler washout.

Not much could be done about this in the 1920s, but after 1930 and the availability of the practical diesel engine in small locomotive sizes it became possible to start replacing many small intermittently used engines with diesels. Small shunters are workable, as are light railcars for low-traffic lines. Only the USA really tries to build many big diesel locos at this time though.

After WWII, crew costs are very expensive, many railways are in ruins, and it's both an economic time to avoid steam and a rebuilding opportunity to do so. So some countries (US, German), strong in diesel knowledge, go for diesels, others (France) choose electricity. The UK unusually sticks with coal for another decade or so, because coal is native and cheap, oil is imported and expensive. But even then, it's the large locos that stay with steam and the railcars go to diesel. Similar economics operate in Argentina and South Africa. Andy Dingley (talk) 11:08, 3 November 2017 (UTC)[reply]

Zero Living Diet Pt2

I was intrigued by the question above. Unless I missed some nuance in the question, my immediate thought was "milk and honey". Neither of these has ever "lived". Sure they were produced by living creatures but they in themselves are not considered alive. Would this fit the OPs question? 185.217.68.208 (talk) 07:12, 30 October 2017 (UTC)[reply]

You'd have to ask the OP (193.64.221.25 (talk · contribs)) that question. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:31, 30 October 2017 (UTC)[reply]

Both of those things are mode from living things.

~~Honey is made from pollen. Pollen was certainly once alive.~~

Milk is less obvious, but it must ultimately came from whatever the cow ate. (Probably grass? Or corn?)

Of course, as Bugs points out, you'd have to ask the guy who wrote the original question if that "counts" for his purposes. ApLundell (talk) 20:50, 30 October 2017 (UTC)[reply]

Yes. It would be nice if he would come back here and Finnish. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:05, 31 October 2017 (UTC)[reply]

Point of order: honey is not made from pollen, it is (most often*) made from nectar. Although nectar is produced by flowering plants, it is not alive in the sense of any of the mainstream Life#Definitions. It's just sugar water, it's no more "alive" than a human's urine or sweat is alive. *Honey is mostly made from nectar, but it can have other ingredients too: honeydew, which is the excreta of some insects, and sweat, e.g. that honey made by sweat bees. SemanticMantis (talk) 18:12, 1 November 2017 (UTC)[reply]

Honey is 80% sugar. The milk is made from the food the cow has eaten. --Hans Haase (有问题吗) 09:20, 2 November 2017 (UTC)[reply]

Moist sodium chloride density data

What data sources are available for the density of moist ordinary salt (sodium chloride) samples as a function of water content and perhaps porosity or void fraction? (Thanks)--82.137.11.59 (talk) 10:43, 30 October 2017 (UTC)[reply]

At Manley’s Technology of Biscuits, Crackers and Cookies you can see the bulk density of granular dry salt 1.22 to 1.32. Using this and the density of sodium chloride crystals of 2.165, you could work out the void space that could contain water and then work out how much water would add what weight, and so get a new density for damp salt. See Bulk density to read about issues to do with density. Graeme Bartlett (talk) 12:02, 30 October 2017 (UTC)[reply]

It's not quite that simple, because some of the water will dissolve some of the salt and form a saturated brine. Because of this, the relationship is likely to be highly non-linear, and just a raw calculation of "filling the void space with water" is unlikely to work; it would work for an insoluble solid like sand, but for salt it gets quite messy to work it out by calculation. You could get a number assuming simply filling in the void space; but that number would bear little connection to the actual denisty. --Jayron 32 12:12, 30 October 2017 (UTC)[reply]

Perhaps predetermining porosity of dry solid salt with liquids like mercury would be a workable variant? Or perhaps checking the plausibility of the assumption that solid dry salt has near zero porosity? An other aspect I think it should be considered and had in mind when formulating the above question is water activity in humid solid salt! I have put the question mainly to address the issue of water activity in this solid substance and to check the degree of non-ideality of the water salt solid mixture as non-ideal solution!

Considering these aspects, another question arises: How can the brine content in the possible void spaces in solid salt be determined?(Thanks)--82.137.14.216 (talk) 13:35, 30 October 2017 (UTC)[reply]

Sodium chloride, thankfully, has a relatively flat solubility curve, so the density of saturated brine is fairly constant at all temperatures from the freezing to the boiling point, 1.202 grams/mL That may be useful. --Jayron 32 15:37, 30 October 2017 (UTC)[reply]

Salt is expected to be sold dry. Normally it does not absorb water from the atmosphere unless it is very humid.[2] The density of bulk depends on how it is handled.

Isn't the rate of change in density with respect to the propotion of water a linear relationship at constant temperature and pressure, in the special case where the solution is saturated? Should the density lie on a straight line between the density at a concentration of 359 g/L and the density of pure salt at 2.165 g/mL? It could also depend on a energy minimum, whether or not the system has an energetic preference for a certain amount of water to be incorporated. Plasmic Physics (talk) 19:23, 30 October 2017 (UTC)[reply]

What's the average or median tidal range of the coast of the World Ocean?

For some reasonable definition of coastline and ocean. I always liked "where mean water level = mean sea level". Do small islands change the answer much through sheer numbers and often being far offshore where tides are smaller? Sagittarian Milky Way (talk) 14:03, 30 October 2017 (UTC)[reply]

There may be a real number for this, but I can't find anyone that has actually calculated it. I've checked several likely google searches, and I can't find anywhere that anyone has ever calculated a worldwide mean tide. The variation is highly dependent on where and when the tide is measured. Hypothetically it may be calculable. Realistically, I can't find any reference to help you figure it out. --Jayron 32 15:35, 30 October 2017 (UTC)[reply]

Sorry, maybe I'm just being dense. Are you asking about the average (mean) difference in height between high and low tide, based on the sample of all the coastlines in the world? The coastline paradox still comes back to bite you, right? Whatever unit you use to determine how many points to measure (every x miles or millimeters of coastline) will affect your answer with the added bonus that the tides also affect some portion of river's edge deeper inland (as with a tidal bore). Matt Deres (talk) 16:31, 30 October 2017 (UTC)[reply]

Right. High seas are generally 200 nautical miles from a line that can shortcut capes ≤24 nautical miles apart if semicircle between capes ≤ area than actual bay which seems a reasonable finition of coastline but as Jayron says any definition at all seems hard to find. Sagittarian Milky Way (talk) 14:35, 31 October 2017 (UTC)[reply]

far offshore where tides are smaller - I would have thought this was "obviously" wrong because outside of areas where water flow is restricted (e.g. Gibraltar is a small passage to the Mediterranean Sea), sea level would simply follow the equipotential of gravitational energy (IIRC if you assume two point-like masses at the centers of Earth and Moon, it is an ellipse). It turns out that is not the case (example: the Azores have much less tide than Lisbon at the same latitude).

This and that indicates that the tide level is a matter of forced oscillation of the water masses in the ocean basins. It is therefore unlikely that there is an easy way to compute tide height at any given location.

You could pull a database of historical tide heights at a lot of locations where that is measured and average them, hoping that it gives a good proxy of the average tidal height (it probably isn't; for instance, ports are at places where tide is low and measurements are done where people are interested to have the data i.e. at ports). I was initially hopeful to find this in a reasonable format for free on the web, but my enthusiasm dissipated after reading this. The closest I found is [3] but that is a pdf format probably impossible to feed to a program. Tigraan^{Click here to contact me} 18:31, 30 October 2017 (UTC)[reply]

An OCR program could pull (digitize) the tide data from the pdf tables but the same data is more readily available ready digitized at [4]. Coastlines may be drawn at Mean High Water (on maps and charts), at Mean Sea Level (on maps showing sea depth) or at Lowest Astronomical Tide (on nautical charts), see Tide#Definitions. Harmonic analysis of tides was introduced in the 1860s by William Thomson (titled "Lord Kelvin" after the river near his laboratory) who built impressive mechanical Tide-predicting machines that employed Ball-and-disk integrators. Harmonic analysis offers the means to subtract all the oscillatory terms of a long-term (19-year, see Metonic cycle) Fourier series analysis to leave only the zeroth term corresponding to the mathematical average. Tidal prediction data thus obtained were kept secret during WW1 and WW2, which is understandable, were then made public, but then in the USA were removed from the public domain after the fact by SCOTUS in Golan v. Holder in 2012 - a ruling on which the WMF in collaboration with the EFF had words to say. Blooteuth (talk) 20:15, 30 October 2017 (UTC)[reply]

As I understand it, and this seems to be supported by our article, Golan v. Holder did not remove anything from the public domain. It simply affirmed the removal from the public domain by the Act in question. Quite a few parties felt the removal was unconstitutional in some way, but few disputed that the Act in question claimed to do so. Note also while a district court had initially found in favour of the constitutional claim, this had already been reversed by a circuit court before it came to the Supreme Court. Incidentally, in case there's some confusion remember that there is a difference between something being in the public domain, which generally refers to copyright and definitely does in the court case in question, and whether something is a classified/secret or public information. (Both can restrict access to information in various ways, but the manner of these restrictions is often quite different, hence they are not normally treated the same.) A point of note, while this isn't legal advice, if a work received an authorised publication in the US prior to 1923, so anything which was published during WW1, it is fairly unlikely it is not in the public domain [5] Copyright law of the United States#Works created before 1978. Nil Einne (talk) 12:11, 31 October 2017 (UTC)[reply]

I realised I made a mistake in my above comment. The publication doesn't have to have been in the US. Also I should mention that there are some limited exceptions for non English works. Sorry for any confusion that resulted. Nil Einne (talk) 11:06, 3 November 2017 (UTC)[reply]

Thomson's tide predicting machine didn't need to use the ball and disc integrators. They were used in the first of the two machines, the harmonic analyser. Once the constants had been determined by this, the prediction machines which then produced the various tide tables could be a lot simpler: it was largely based on slotted yoke sine generators, a single string to add their values, and varying diameter pulleys to adjust the magnitude of the components. Andy Dingley (talk) 15:51, 31 October 2017 (UTC)[reply]

Note that while mean and median aren't the same, mathematically, they may work out to be similar in the case of a sinusoidal wave, like tides. See measures of central tendency. StuRat (talk) 04:16, 31 October 2017 (UTC)[reply]

If the tides were perfectly sinusoidal (they only approximate that) there's no reason why mean and median tidal ranges must be the same. The rare points about 40 feet above average have disproportionate effect on the average but little effect on the median while points with little tide like the Mediterranean and Gulf of Mexico are common but can only be a handful of feet below average cause tidal range can't be below 0. It seems like one of these factors would win and make the mean and median not identical. Sagittarian Milky Way (talk) 14:35, 31 October 2017 (UTC)[reply]

Finding Voyager 1 goes dark

When Voyager 1 runs out of power and we develop manned space travel past our planet's orbit, how easy will it be to find Voyager 1 to study it? I realize this is sort of crystal balling but maybe someone has thought of it before and did some research. †dismas†|^(talk) 18:34, 30 October 2017 (UTC)[reply]

Well, we know the trajectory quite precisely, but the problem is that the Trans-Neptunian objects aren't comprehensively mapped out, and there may be large objects Voyager will encounter. Now the chances of an impact are extremely small, but even the most modest of gravitational deflection could have a major effect on the location, over centuries. So, the time period elapsed would be important in knowing how great the error will be, and we also don't know how sophisticated our scanning devices will be by then. There's also the political climate to consider in the future. That is, would they really think retrieving Voyager was a good use of taxpayer money ? So yes, unfortunately, this does get into crystal ball category. StuRat (talk) 19:08, 30 October 2017 (UTC)[reply]

The two Voyager missions will start the process of shutting down according to the schedule here. According to that webpage (from NASA) in 2020-2021, NASA will begin powering down various science experiments on the probes to conserve fuel, and all science experiments will cease by 2025, however NASA will still receive telemetry data from the probes until about 2036, when all power to the probes will fail completely. --Jayron 32 19:19, 30 October 2017 (UTC)[reply]

Also, you mentioned manned space travel, but such a task would be far better suited to a unmanned spacecraft. That is, unless we develop some way to get there much faster, such a mission would take years, and a human would need food, water, air, heat, etc., for all that time. (Considering that they've been flying away from Earth for over 40 years now, even if we had some way to get there 10 times as fast, that would be 4 years, and by then they would have moved on a bit further, and then we have to add the time to locate and retrieve the ship, and the return trip, so we'd be talking about some 9 years.) StuRat (talk) 19:31, 30 October 2017 (UTC)[reply]

There was an XKCD "Whatif" column about retrieving Voyager. [6] Unfortunately, it's one of the early ones that's not really referenced. But you can usually trust Randall Munroe's math. ApLundell (talk) 20:29, 30 October 2017 (UTC)[reply]

Excellent info. But what if a chemical rocket with planetary gravity assists was used to get part of the way there, with fast acceleration, then ejected, using an ion engine for the rest ? Hopefully that combo would cut the time down somewhat. StuRat (talk) 21:06, 30 October 2017 (UTC)[reply]

If we don't have to wait until it goes dark then I think two missions would be most realistic. Mission one catches up to Voyager 1 when it's still transmitting, grabs hold of it, and brings enough reliable resources to keep transmitting for far longer. Mission two launches when rocket technology is good enough for a return mission. PrimeHunter (talk) 21:14, 30 October 2017 (UTC)[reply]

This is no "crystal balling" but plain madness! Are you aware of the pricetags of such projects? In case you are a multi-billionair dump you money where you like, else get sober and think again about asking this. --Kharon (talk) 02:07, 31 October 2017 (UTC)[reply]

Actually cost may be less of a factor than you would think, if the cost of space travel starts to steadily decrease. Give it a century, and such a thing might be financially feasible. In particular, at some point I would expect space probes to start being mass produced, and no longer cost billions each. StuRat (talk) 04:20, 31 October 2017 (UTC)[reply]

Even so, such an exercise would be pretty pointless. I'm struggling to think of anything that could be usefully gained from physically studying Voyager 1.--Shantavira|^{feed me} 07:55, 31 October 2017 (UTC)[reply]

The effects on technology of long-time exposure to interstellar space? If the return cost becomes low enough then you might want that before launching more expensive interstellar missions, but it would probably be easier to extrapolate from short-term exposure. Future space historians may also be interested. It would be a nice museum exhibition. PrimeHunter (talk) 10:59, 31 October 2017 (UTC)[reply]

I think some exogenous point is needed. A typical sci-fi explanation might be that when the probe gets X distance from the system, aliens are allowed by their procedures to reveal their existence ... and tell the puny humans that if anything man-made gets Y distance away they will be annihilated. Apart from that, you're basically waiting for ultra-cheap space travel and a museum with too much money. Wnt (talk) 11:52, 31 October 2017 (UTC)[reply]

See Mary Rose and Star Trek: The Motion Picture for possibilities. Dbfirs 12:11, 31 October 2017 (UTC)[reply]

Okay, so nothing about finding it. Got it. Thanks, everyone. †dismas†|^(talk) 23:41, 31 October 2017 (UTC)[reply]

Well tracking a path and calculation a distance with a given speed and time is what is done in astronomy every day. If they can see and track an Asteroid 10 million miles away and predict how far from earth it will pass where and when they are probably capable to predict where a satellite they exactly piloted for years will exactly be in the future. Very precise with an error of maybe less than 5km. Does this answer how to find it for you? --Kharon (talk) 04:36, 1 November 2017 (UTC)[reply]

See Asteroid#Computerized methods. Many asteroids are not known about until they approach Earth and become visible. The only way then to avoid losing track of them is to keep them under constant observation. 80.5.88.70 (talk) 09:29, 1 November 2017 (UTC)[reply]

... and see n-body problem for some of the complications. Dbfirs 17:42, 1 November 2017 (UTC)[reply]

@Dismas: I am assuming that by "find it" you actually mean the challenge in just locating the craft, not the difficulties associated with the mission (manned or unmanned) to rendezvous and return with Voyager 1. If I were to reach for a Fermi estimate, I might look at the Pioneer anomaly to get an order-of-magnitude for the uncertainty in location. (Brief background—like Voyager 1 and 2, the Pioneer 10 and 11 probes followed long trajectories out of the Solar System; like the Voyager craft, the Pioneer probes carried radioisotope thermoelectric generators to produce electricity. For at least the last three or four decades, the Pioneer probes exhibited a minuscule but unexpected acceleration, dubbed the Pioneer anomaly. Various hypotheses were offered to explain the acceleration; in the last few years, it's generally been agreed that it is the result of radiation pressure. Heat radiated from the thermal generator provides a weak unbalanced thrust to the craft.) The acceleration there is on the order of 1 km/h per year, or roughly 10 000 km/year per year. If Voyager 1 experienced the same sort of acceleration, after 1 year it would be about 5 000 kilometers away from where we would expect it to be. After 100 years, it would be about 50 million kilometers out of place.

So then the question becomes, at what distance and using what technology can we detect a Voyager-sized object at those sorts of distances? I'll throw the field open here. Do you use radar? Infrared? Something else? (Thinking a bit more, the Voyager RTGs used Pu-238 fuel with a half-life of 88 years, so that source of anomalous acceleration would have faded quite a bit after the first few centuries. But that also means that detection by heat signature would be less effective as the core cools. One hand giveth, the other taketh away.) What sort of objects are going to be 'out there' in interstellar space, and how hard will it be to distinguish Voyager from them? TenOfAllTrades(talk) 01:36, 3 November 2017 (UTC) (math corrected TenOfAllTrades(talk) 11:57, 3 November 2017 (UTC))[reply]

Thank you! The last couple answers helped sate my curiosity over this question. †dismas†|^(talk) 20:54, 3 November 2017 (UTC)[reply]

October 31

Math used in doctoral-level natural sciences

A question on the math desk about math in med school raised this question in my mind: What types of math are used in (a) astronomy, (b) physics, (c) chemistry, (d) biology, and (e) geology? (I presume that for physics the answer is “all of it except number theory”, so I’m more interested in the answers for the others.) Loraof (talk) 00:53, 31 October 2017 (UTC)[reply]

Stoichiometry and Statistics are special tools of choice in chemistry and biology. In Astronomy Geometry (yes that counts as math) has wide application but then the "included" Astrophysics is physics (and chemistry) too! Like in Astronomy physic science is used as base in every "natural" science, so what applies to physics applies to all the others you mentioned at some point. --Kharon (talk) 01:50, 31 October 2017 (UTC)[reply]

Some of the nastier math in biology is encountered in the context of Ronald Fisher regarding population genetics. But some serious computational issues go into things like protein structure prediction. Of course this is not an exhaustive list. Wnt (talk) 02:18, 31 October 2017 (UTC)[reply]

It depends on which specific subfield you are working in; for many fields of Chemistry, daily working knowledge of mathematics beyond basic algebra probably isn't necessary, though for some others being able to understand, calculus is essential, such as the fourier transform or partial differential equations involved in Lagrangian mechanics and Hamiltonian mechanics, especially in people who work in physical chemistry. --Jayron 32 10:48, 31 October 2017 (UTC)[reply]

Hah! Biology even uses number theory. (But so does physics, actually.) Looie496 (talk) 12:29, 31 October 2017 (UTC)[reply]

How is number theory used? Loraof (talk) 14:49, 31 October 2017 (UTC)[reply]

Can't speak for biology, but a good summary for physics would be Matilde Marcolli's paper Number Theory in Physics. A nice toy model would be the primon gas, and one can then look at the physics of the Riemann hypothesis. Double sharp (talk) 15:13, 31 October 2017 (UTC)[reply]

This speaks for biology. As does this. --Jayron 32 15:37, 31 October 2017 (UTC)[reply]

Additionally for physics, aspects of number theory especially with renormalization of divergent series, show up all over physics. Perhaps most famously, the sum of all integers shows up in calculations involving quantum mechanics. The series sums to infinity, renormalization allows the use of -1/12 as the value of the function, and the use of that value in place of the infinite series produces experimentally verifiable results. --Jayron 32 15:56, 31 October 2017 (UTC)[reply]

Thank you! I'd consider divergent series to be more analysis than number theory in general, but divergent Dirichlet series certainly have one foot in each. And of course, the renormalisation goes straight back to the ζ function, and the proof going through that and its relationship to the η function showing ζ(−1) = −1/12 is exactly where the grain of truth in the justly criticised Numberphile demonstration lies. Double sharp (talk) 07:11, 1 November 2017 (UTC)[reply]

Well, I think such criticisms are holding a pop-math youtube channel a bit too responsible for what isn't wrong if so much as oversimplified. Really it comes down to the fact that we have different defitions for what "equals" means, and usually (but not always) those definitions align in ways that make us forget that occasionally they don't. The sum of the integers is an example of that difference. When we say "f(x) = y" we mean both :

performing function "f" as a task will produce result "y", AND:
we can substitute "y" for "f(x)" into other situations and get valid results.

For most math, that works fine: for example, we can have two equations: y = x² AND the x+1 = 4. We can solve the second function to get x = 3, then substitute that value into the first to get y = 9, which is a perfectly valid result. For math involving infinite series, we get the paradoxical result that if we solve x = 1 + 2 + 3 + 4 + .... such that we get x = ∞, HOWEVER, if we substitute ∞ into a second equation we get nonsense that does not match, say, an actual observation of nature. The interesting thing about the -1/12 thing is that if we substitute -1/12 into equations where that particular infinite series shows up, we get observationally verified results, that is real physical process obey theoretical equations that use the infinite sum of integers if we substitute -1/12 for that series. Consistently. So, in one sense, it is equal to it because you can swap the one for the other and get true things. That's one thing that equals means. Unfortunately, it doesn't match the other part of being equals, which is to literally perform the operation on one side. So, it's not wrong. It's just a highly speciallized application. --Jayron 32 11:27, 1 November 2017 (UTC)[reply]

Thanks for that clear explanation, Jayron. Now I finally understand what’s going on with that – there’s a difference between the two meanings of “f(x) = y”. Loraof (talk) 02:13, 2 November 2017 (UTC)[reply]

We're not quite replacing that series by −⁠112⁠. It's the finite part of the result that goes to −⁠112⁠. There's a good explanation on Math Stack Exchange here: basically, for stuff like the Casimir effect where this series comes up, there is an exponentially decreasing regulator making each term not n but ne^−εn, and the original series is obtained in the limit when ε approaches 0. If you sum this, you get ⁠e^ε(e^ε − 1)²⁠, and a bit of Laurent series expansion leads to the result ⁠1ε²⁠ − ⁠112⁠ + ⁠ε²240⁠ + O(ε⁴). In the limit, the third and all succeeding terms go to zero, the −⁠112⁠ stays constant (of course), and crucially, the first term that causes the divergence is cancelled by a local counterterm representing vacuum energy – for the case of the Casimir effect, the sum of the zero-point energies if the region were not bounded by those metal plates. Since this is physics, ε has dimensions and the terms can be separated like that without affecting each other.

So it is not quite that we magically waive the usual meaning of "equals", but that for physics applications the divergent parts of the series are cancelled out and only −1⁄12 matters in the limit that we are interested in. Double sharp (talk) 12:46, 2 November 2017 (UTC)[reply]

That was a really good explanation. Thanks! --Jayron 32 15:42, 2 November 2017 (UTC)[reply]

You're welcome, but the major credit goes to Luboš Motl from Stack Exchange: I merely summarised the important points and left out the details that were not pertinent to the main issue. Double sharp (talk) 16:28, 2 November 2017 (UTC)[reply]

Just for the sake of nitpicking: Since this is physics, ε has dimensions and the terms can be separated like that without affecting each other is not really true (epsilon is adimensional here) though it captures the idea. We are working with a perturbation series in a small exponent; the idea is that the results of our computations "work" as the exponent approaches zero, but in particular they must be true with arbitrary accuracy for infinitely many values of the small exponent; or formally, that for any given precision, you can find any number of values epsilon such that the result is within the precision (it is pretty much the definition of a limit (mathematics)). This is what authorizes us to say the different terms do not interfere, as if they were of different dimensions (but if they were, it would not be licit to sum them), because two powers series with the same form are equal iff. each pair of prefactors is equal (under certain mathematical assumptions that we don't care about here). Tigraan^{Click here to contact me} 16:56, 3 November 2017 (UTC)[reply]

Motl "cheated" here a little, and I followed him, since this wasn't quite the main point and as you say, the idea is captured: but it seems that thanks to you we are now building a very comprehensible series of explanations of this all-too-often touted as incomprehensible result! Thank you for that! Double sharp (talk) 04:20, 5 November 2017 (UTC)[reply]

My field of biology is ecology, and I study things like population dynamics and population ecology. Mostly the math I use is related to dynamical systems theory, including stochastic processes and statistical distributions, but also more pedestrian things like linear algebra and basic calculus. Some of my colleagues get heavily in to PDE, and various types of Matrix_population_models are also very popular. Some concepts from information theory get some play too, see e.g. species evenness. Many of the big names in my field (e.g. Simon Levin) have PhDs in math. Then there's a whole world of tools from statistics (e.g. Bayesian inference, General linear models, regression, curve fitting etc.) applied to ecology. Really all the fields you list make some use of mathematical modeling, broadly speaking. SemanticMantis (talk) 15:02, 31 October 2017 (UTC)[reply]

How about the use of mathematical logic and fuzzy logic in physics and biology?--82.137.10.247 (talk) 13:50, 2 November 2017 (UTC)[reply]

Here is a silly conference in French with logical gates made of carnivorous plants. Strangely enough, the speaker does not put that area of research on his professional webpage. Tigraan^{Click here to contact me} 14:13, 2 November 2017 (UTC)[reply]

You might not call it silly when Dionaea muscipula realize their collective processing ability to calculate Cryptographic hash functions such as SHA-256 without electricity, and compete with humans at mining bitcoins. Blooteuth (talk) 15:00, 2 November 2017 (UTC)[reply]

Well, it is a serious conference about a silly subject. Right now, those are about 10^10 slower in FLOPS than a Raspberry Pi for about ten times the dimensions, so I wouldn't be too worried. Tigraan^{Click here to contact me} 15:32, 2 November 2017 (UTC)[reply]

I'm not sure that's ready for final implementation, but it's a SEED of an IDEA. DMacks (talk) 17:37, 2 November 2017 (UTC)[reply]

We have a whole Biological computing article. DMacks (talk) 17:37, 2 November 2017 (UTC)[reply]

Lots of mathematical logic at play in analyzing gene expression and gene regulation. Similar to how simple circuits embody logic, so can metabolic networks and other biological processes. See e.g. here [7] for some scholarly research on the logic and combinatorial control using mRNA. SemanticMantis (talk) 15:34, 2 November 2017 (UTC)[reply]

Molecular Summary Table

Dear all,

first of all I apologize for my bad English. I will improve it. I´m still new here at wikipedia and my instruction consists in publishing scientifical articles. Most of them contain chemical infoboxes (similar like drugboxes, enzymes)calles "molecular summary table". I tried everything to publish the following table but it doesn´t work.

It´s about the following infobox:

https://de.wikipedia.org/wiki/Wikipedia:Redaktion_Chemie#/media/File:Wikipedia_Support_2.jpg

The molecular summary table is almost published on a german wikipedia support page. I need urgent help in converting this table into wiki syntax. I would be very grateful for support!

Thanks and best regards

--Gunnar Römer (talk) 13:13, 31 October 2017 (UTC)[reply]

The better place to bring this up may be Wikipedia talk:WikiProject Chemicals. They might be better suited towards helping you in this highly technical question. --Jayron 32 13:25, 31 October 2017 (UTC)[reply]

Thank you! — Preceding unsigned comment added by Gunnar Römer (talk • contribs) 14:00, 31 October 2017 (UTC)[reply]

Moved to Wikipedia talk:WikiProject Chemicals § Molecular Summary Table

IEC standards list

Hi! How can I find a complete list of IEC standards?

I searched in IEC website, but I couldn't find that list.--92.50.40.2 (talk) 15:54, 31 October 2017 (UTC)[reply]

Do you mean the List of International Electrotechnical Commission standards? --Jayron 32 18:49, 31 October 2017 (UTC)[reply]

Our list is incomplete. These standard institutions usually forbid copying anything, maybe even a collective list, because they finance themselves by selling their standard definition papers or digital e-papers. In fact you usually already have to pay to just enter their "shop" aka subscribe to some access plan, so you may be able to see the list, if you start paying them! They have a monopoly and they act like it. Of course usually for breathtaking prices. The best chance to access, to the complete list and all standards, for private persons are usually Libraries in big cities or cities with a fitting university. They usually have all standard papers. Chances are high tho you may only read them in the Library but not lend them out. --Kharon (talk) 19:51, 31 October 2017 (UTC)[reply]

IEC though is typically one of the lowest priced sources for standards, and they often duplicate standards issued by other bodies (for example UL). AFAIK they don't charge any fee to browse the standards available from their web store. They even make some material, like the International Electrotechnical Vocabulary available gratis. I don't find any comprehensive list of standards on the website, but there is a of subcommittees with links to the publications available from each subcommittee. The Photon (talk) 05:11, 2 November 2017 (UTC)[reply]

November 1

Gigantic Chinese finger trap

It is a very clever way to grab the end of a cable to thread it through a tube or tunnel. It works like a Chinese finger trap. Is there a general name for this sort of weave or shape or something? The commons cat contains finger traps as well as a traction device using the same shape. It would be nice to have some sort of proper name. Anyone? Anna Frodesiak (talk) 02:06, 1 November 2017 (UTC)[reply]

Is it a type of hollow Rope#Braided rope? Anna Frodesiak (talk) 02:22, 1 November 2017 (UTC)[reply]

A small version of this tool has been called a rope trap, larger ones are called a wire rope puller or a towing sock. Naturally there is also an article about the original Chinese finger trap. Blooteuth (talk) 02:27, 1 November 2017 (UTC)[reply]

Thank you again, my friend. I have therefore just stubbed Towing sock. Now, I will attempt to find a non-spammy ref. Anna Frodesiak (talk) 03:00, 1 November 2017 (UTC)[reply]

A cable head is a different device with a similar capability. Nimur (talk) 03:28, 1 November 2017 (UTC)[reply]

Similar indeed, Nimur. I wonder how they affix the cable to it. I see pics on the net. I hope that's it. It looks like Captain Hook's arm end without the hook. Is that it? Anna Frodesiak (talk) 03:53, 1 November 2017 (UTC)[reply]

I'd like to add to the the article (Towing sock) the fact that there is a loopy thing on the end. It probably has a name but I don't know what it is. Anna Frodesiak (talk) 04:02, 1 November 2017 (UTC)[reply]

This is useless for professional application because cables meant for tubes and tunnels are either electric power cables or communication cables, either electrical or fiber. All these cables are absolutely not suited for tension so pulling them over longer distances will damage them because at some point, when you pull for example 100 meters, you have to pull the weight of a 100 meters long cable and the friction on top which accumulates to forces beyond the material capabilities. Its a smart idea as concept but in that application not thought thru to the end, because these cables are in fact surprisingly fragile. Because this is not used anywhere obviously it can not have a common name. --Kharon (talk) 04:25, 1 November 2017 (UTC)[reply]

Somehow the electricians here get long runs of cables fed through pre-buried conduit. They might use devices like this for pulling cables with 8000 lbs of force at 6 ft/minute, and associated lube to make it easier and a companion pusher to feed at a rate matched to the puller. They also might use a "pulling sock" for some cases, that sounds like the towing sock. This one (also 8000 lbs at 6 ft/minute...seems like a standard?) says it's for conduit pulls of up to "4 x 500mcm Copper Cables, 800 ft. w/(3) 90 deg. Bends, 3 x 1000mcm Copper Cables, 750 ft. w/(4) 90 deg. Bends, 4 x 750mcm Copper Cables, 1200 ft. w/(2) 90 deg. Bends". That's a lot of cable weight! DMacks (talk) 04:45, 1 November 2017 (UTC)[reply]

And yet I've seen (I used to work for BT) such "finger traps" being used regularly to haul cables, and to haul ashore undersea cables. Large cables are designed to survive the tension of pulling them into place. It's the only way to install them. Andy Dingley (talk) 10:21, 1 November 2017 (UTC)[reply]

Hi Kharon. It most certainly is used. The one pictured was in use just last week. The cable in the photo is probably around 10cm in diameter, by the way, and didn't look fragile. Also, it does have a common name because companies sell them with that name. Best wishes and thanks for the input. Anna Frodesiak (talk) 13:11, 1 November 2017 (UTC)[reply]

Thinking about this problem I was wondering if sound could help as in the way one can use it to make things creep up a surface. I don't suppose it would help get a cable through a conduit never mind round a corner, but do you know if they have tried using vibrations to reduce the friction whilst pulling cables? Dmcq (talk) 13:23, 1 November 2017 (UTC)[reply]

@Anna Frodesiak: I dont doubt its used. Its just no professional tool - not even if you can buy it with a big lable "professional towing sock" on it. I also doubt the claim of Andy Dingley, that these are used on Submarine fiber cables since these are exeptional fragile and expensive. I once read the history of the crazy struggle to lay out the first transatlantic communication cables and today huge constructional efford is made to gently let the cable down from the ship to the seabed, making sure even the cables own weight is not carried by the cable itself, so additional "pulling" at one end seems out of question. --Kharon (talk) 17:25, 1 November 2017 (UTC)[reply]

Also from the Schlumberger website, here's an old article: Coiled Tubing Takes Center Stage (1994). Modern technology makes it possible to steer a cable through sharp angles, over miles of borehole. Some of the most sophisticated applications are in the petroleum and natural gas industry; but the same technologies can be used for electrical and data cables, undersea cables, and so on. The ostensibly simple task of threading a "wire" through a "hole" is confounded by the incredible technical challenges of complicated "wires" and complicated "holes." For perspective - a modern drillstring might be several miles long, may be carrying sophisticated scientific instruments like a gamma-ray spectrometer, may be mechanically coupled to a drill bit that can cut through solid rock, and may be subjected to heats and pressures of geological magnitude. Meanwhile, civil engineers and construction crews can thread high-voltage cables and high-capacity water and gas pipelines through boreholes drilled underneath roadways; and can repair and replace existing infrastructure and piplines; all without ever compromising the structural integrity or interfering with the road traffic or structures on the surface. Cables, pipes, and tubes are neat - they're a lot more high-tech than many people realize! Nimur (talk) 17:31, 1 November 2017 (UTC)[reply]

(edit conflict)Fibre is quite fragile and is normally blown with compressed air in terrestrial installations. This can't be done for long stretches under the sea, of course, so the conduit or other support has to take the strain. Dbfirs 17:37, 1 November 2017 (UTC)[reply]

Yes, you can see an example here from NZ [8]. Nil Einne (talk) 07:01, 2 November 2017 (UTC)[reply]

At Submarine communications cable it says about a one inch cable weighing about 2.5 tons a mile, since the Atlantic would be a couple of miles at least at some point going across and the water won't buoy up a cable much it must be able to withstand a number of tons weight pull. Especially if repairing means dragging up a piece to the surface. So delicate is probably rather a relative term. Dmcq (talk) 17:59, 1 November 2017 (UTC)[reply]

It's the stranded steel wire that takes the strain, of course, not the fibre. Dbfirs 18:04, 1 November 2017 (UTC)[reply]

http://www.kis-orca.eu/subsea-cables/design#.WfoNEVu0NEY

20–70 tons tensile strength. Andy Dingley (talk) 18:07, 1 November 2017 (UTC)[reply]

Hey Mr. Cherrypicker, next time please present the hole cake:

"The heaviest form of armoured cable may have in excess of 70 tonnes breaking strength. While the cable may only break or part at high tensions, damage to the optical path or to the electrical insulation (the polyethylene) can occur at much lower tensions" --Kharon (talk) 23:21, 1 November 2017 (UTC)[reply]

There are two open threads on this RefDesk where you are spouting your own subjective opinion as fact, and in this case over an external source. I take your comments here, particularly the insinuation that I am lying, very much as a personal attack. Now cut it out. Andy Dingley (talk) 23:46, 1 November 2017 (UTC)[reply]

Kharon, a simple search for 'cable pulling tension' finds many, many, many, many, many results discussing maximum pulling tensions and related issues for cables, including methods to calculate pulling tensions for cables under various conditions and commercial software to help with plans, and while some look like they may be directed at smaller home runs, others at stuff like "paper mill and your client needs a 400A, 15kV feeder": [9], [10], [11] [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24] [25], [26], [27] (also look at the next page), [28], [29] (see also page 70, 58 and 59).

A number of these are from cable manufacturers themselves, and some reference a study by the Insulated Cable Engineers Association, or other studies or publications (e.g. from the IEEE or AEIC). At least some of these specifically mention or deal with a basketweave (or basket or mesh or wiremesh) grip which from Google Image search results (well also at least one of the above results) e.g. [30] [31] [32] [33], seems to be the same sort of thing we are dealing with here.

Others refer to a pulling eye which is different and only attaches to the real end of the cable [34] [35] [36] (some sources also suggest you can attach one to a basketweave grip although I'm a bit confused by this since most sources seem to show that the basket grip already has a buil in grip. Interesting, a pulling eye generally allows greater pulling tension but I don't think this is because of less damage to the cable, actually you still need to take care you don't exceed whatever it allowed for your cable. Instead I'm fairly sure it's just to do with what the equipment can survive, see the earlier results.

Note a pulling eye is different from a pulling grip, Corning Optical and others seems to use pulling grip to include what others call a basketweave or basket grip [37] [38] (which incidentally is of course another manufacturer who doesn't seem to think there's anything wrong with such devices in the right circumstances).

Anyway, so either all of these are super unprofessional as you suggest, or as others have suggested you don't know what you're talking about.

Nil Einne (talk) 13:18, 2 November 2017 (UTC)[reply]

Speaking of omitting context to misconstrue meaning, Kharon, you selectively included only part of the additional phrase. As such, you are using information about breakage by bending rather than tensile strength. DMacks (talk) 07:12, 2 November 2017 (UTC)[reply]

Thank you all for the very educational input.

Can anyone find a non-spammy ref for Towing sock? I'd hate to leave it unsourced. I tried searching .edu, .gov, and .org sites, but no luck. Anna Frodesiak (talk) 21:26, 1 November 2017 (UTC)[reply]

Hey, User:Anna Frodesiak, interesting find, and thanks for your work on this! I think some redirects are in order, and may also help you in your searches for sources: check out this commercial site [39] selling similar products as "Strain-relief grips." Sounds a bit more formal, but note the search term there is "chinese fingers"! Cable grip seems to be a general category, of which "chinese finger" is a type. See this google search [40], indicating that "pull[ing] sock" is also used [41]. Here's a "cable pulling grip" [42].

Certainly some of this commercial vendors can help in the the short term as RS that demonstrate this is a thing that has these names. Perhaps some of the names will help you find better RS. SemanticMantis (talk) 22:25, 1 November 2017 (UTC)[reply]

Hi SemanticMantis. Thank you for the thank you. I was happy to stub it. Now, you say Cable grip is the blanket term, but the lead at that article "...A cable grip is a device for propelling a vehicle by attaching to a wire cable..." makes me reluctant to add the term to the towing sock article. Should I though?

About redirects, would you be a dear and add a few that you think would be appropriate? I'm a bit out of my depth on this.

About refs, I'll keep looking, and if you bump into one, please let me know. One would think that NOAA or some US gov powergrid sort of site might mention the thing.

All the best, my friend.

Oh, and the Google link doesn't work for me because I'm in China. I'm stuck using Bing. (Stop laughing. I can feel you laughing. It's tragic, not funny.)

Anna Frodesiak (talk) 08:50, 2 November 2017 (UTC)[reply]

This book [43] Electrical Power Cable Engineering, Third Edition published by CRC Press which I linked above mentions a woven basket grip but doesn't provide that many details. Another book I linked above Cables and Wiring published by Cengage Learning [44] (also look at the next page) calls it either a wire mesh grip or a basket grip (see page 66 and 70) also provides a limited amount of details but does include a diagram. I presume the links are useless to Anna, but maybe they will be useful for others. Nil Einne (talk) 13:18, 2 November 2017 (UTC)[reply]

Thank you Nil Einne and all. I've made the following redirects:

Anna Frodesiak (talk) 23:25, 2 November 2017 (UTC)[reply]

How do photons work to enable visual perception

I'm trying to get a better understanding of how photons work to enable visual perception.

I work at a location nearby an airport. During the day I may look up to the sky and see a plane up in the sky shortly after takeoff. My limited understanding is that photons coming from that plane in the sky and entering into my eye, allowing me to perceive a plane in the sky. If this is correct, I have a few questions to further my understanding:

How do the photons that entered my eye emanate from the plane? I'm assuming that the plane did not create the photons, and that most likely they originated from our Sun. So did they bounce off the earth in the direction of the plan and then bounce off of the plane and go into my eye? If so, how do photons bounce off of the earth? Do they bounce off of the earth the way a laser bounces off of a mirror or do they "scatter" off of earth in all directions? Likewise, with photons reflecting off of the plane - do they scatter in all directions or do they have a more predictable path of travel?

And finally what happens to the photon after it enters my eye? Does the photon pass through? Reflect or scatter back out in another direction? Get changed into an electrical signal and therefor (for lack of a better word) "die" as a photon?

I wouldn't be surprised if full and complete answers to my questions involved long and pronounced explanations. I welcome such, but if it makes it any easier, am really just looking for a general understanding of what is happening as I look up to the sky and perceive things.

128.229.4.2 (talk) 20:08, 1 November 2017 (UTC)[reply]

You could start with Visual system, which says that the photo receptor absorbs the photon. As to your questions about light sources, sunlight can "bounce off" things multiple times. Artificial light can do likewise. Also, a plane has built-in lights. So some of the light you see can be emanating from the plane's lights. But most of it is coming from the sun, either directly or by reflecting off something else. For example, a building with reflective glass windows, where you might see a reflection of the plane (or any object). ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:29, 1 November 2017 (UTC)[reply]

Something else to think about: At or near full moon, the moon is pretty bright. If you're someplace with minimal light pollution, you can see objects in the moonlight. The moon itself emanates no light. Moonlight is totally from reflection, nearly all of that coming from sunlight. So if you see an object in the moonlight, you're seeing it via sunlight bouncing off the moon and then bouncing again off the object and into your eyes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:35, 1 November 2017 (UTC)[reply]

Diffuse and specular reflection from a glossy surface.

This is more a question about Optics than about the human eye specifically, but it's a big question!

Briefly, you're mostly right. The light you see from a plane did not originate from the plane.(Excepting the light from light sources on the plane itself like landing lights.) It's either lit by the sun itself, or from light reflected off the earth. The Difference between photons reflecting like a mirror, or scattering in all directions is the difference between Specular reflections and Diffuse reflections. (The shinier an object is, the more specular reflection will happen.) And yes, the Photoreceptor_cells in your eye can absorb photons. And so can many other things. A black piece of cloth can absorb photons and convert them to heat.

I'm sure my little paragraph here isn't very informative on this huge subject, but the articles I linked are very in depth, and worth reading. ApLundell (talk) 21:26, 1 November 2017 (UTC)[reply]

Agreed. Note also that those articles sometimes talk about light as a wave; see also wave–particle duality for a lot more on that concept. Oh, and also note that some of the incoming light is scattered in the air, not from the Earth's surface. --69.159.60.147 (talk) 21:31, 1 November 2017 (UTC)[reply]

Since no one has yet spoken to the biophysical, neurophysiological and cognitive mechanisms at work with regard to your latter set of questions (regarding what happens once the light enters the eye), and seeing as visual cognition is an area in which I have expertise, I will pick up the description from there. However, owing to time constraints, I may explain this process in small installments over the next couple of days, as this is a deeply complex set of topics--though I will try to keep discussion concentrated on the most top-level processes and try not get caught up in the weeds on the chemistry and neuroscience.

Photons enter the eye through the optic lens, which, in the human eye, is controlled by muscles which flex it in order to focus the light on different portions of the retina, which absorbs the photon. Amongst the matter absorbing these photons are photoreceptive cells, rods and cone cells. These cells are preferentially sensitive to light of varying wavelengths and intensity (see also Photometry (optics) and Luminance). The absorption of photonic energy catalyzes a reaction in a receptive protein molecule, of class known as opsins, creating a chain reaction of protein activity for the purposes of cell signaling. The degree and duration of this stimulus either excites or inhibits the cell, towards a threshold where the cell will be more or less inclined to fire, sending a bioelectrical signal to another kind of specialized nerve cell, as the first step of relaying the signal that carries information as to what has happened with that particular receptor into the optic nerve and ultimately into the brain, where the combined stimulus of all the receptors is amalgamated, filtered and processed to create visual perception and the subjective experience of vision; the higher-level neuroscience, cognitive psychology and metaphysics of the perception are where I will pick up tomorrow. Hope the first part helps for now! Snow ^{let's rap} 07:37, 2 November 2017 (UTC)[reply]

Then, do you know if, what appears to be red to 1 person, could be blue to another, what is blue to another, could be green to a 3rd? Etc. Thanks. 12.130.157.65 (talk) 12:08, 2 November 2017 (UTC).[reply]

That question overlaps two subquestions. An illustrative case is colour blindness, which was scientifically described first at the turn of the 18th century, but certainly existed long before. The first subquestion is whether the eyes of two different individuals have the same physiological response to stimuli - in which case, I cannot answer (beyond the case of colour blindness pathologies). The second is whether the perception of those stimuli is the same, regardless of the physiological response - in which case, there is an abundant literature on the subject in psychology and philosophy: one of the key words is qualia, but that article is a hard read; Color_vision#Subjectivity_of_color_perception may be an easier explanation of why that is even a question. Tigraan^{Click here to contact me} 12:23, 2 November 2017 (UTC)[reply]

Okay, so no part 2 Snow Rise? Anyways, they say when someone is red-green color-blind, they don't see both red and green as red, or both as green, but both as the same reddish-green. But how can we know that? 12.130.157.65 (talk) 11:30, 5 November 2017 (UTC).[reply]

Regarding the behavior of photons, there's a few key things to remember here: Light is light. It is a phenomenon that produces certain data based on the manner in which it is observed. When we ask what light is, the only response is "this phenomenon that produces this data from these observations and experiments". What we then ask is "how do we model light" the answer is "we model it as either a wave or a particle depending on what a particular situation needs". Which is to say "In some situations (i.e. the photoelectric effect), it makes sense to model light as a particle. In other situations (diffraction), it makes sense to model light as a wave". The ontological question (what is light REALLY?) is not something which is particularly relevent or useful in physics, it's a philosophical issue, not a scientific issue. The only thing science does really is create predictive models: a set of laws, theories, equations, etc. which when given a certain input, make accurate predictive outputs. The only reason I bring that up is the implicit problems with discussing quantum phenomena like light, where we're always dealing with switching our brains between thinking of light as a particle, and thinking of it as a wave. In the case of vision, both are really needed here:

Concepts like scattering and diffraction and refraction and the like really make more sense to think about in terms of wave-like properties of light. So when asking "how does this light get to my brain to make an image", many of the phenomena between the object you are looking at, including the way the light is affected by the surfaces, materials, and substances involved simply model better as wave phenomena. Famously, even a single photon obeys the wave patterns, the famous Young's double slit experiment showed that a single particle can be made to split and interfer with itself.
Concepts like how the light interacts with the rod cells and cone cells in the back of the eye to produce an electrochemical signal work better if light is modeled as a particle rather than a wave. That's because fundementally, it involves individual photons of light exciting individual electrons in photoreceptor proteins like rhodopsin in a very one-to-one particle-like manner which cannot adequately be explained by wave behavior.

The thing is, this stuff is really hard in the sense of it is NOT intuitive. Every physicist, chemist, etc. who studies or has to explain this stuff I've ever heard speak on the matter is never comfortable with issues of wave-particle duality because it just doesn't make sense in the "this is what my experience in the world tells me life is like" sense, even the people who do this as a vocation never really come to find it a natural way of thinking. The only reason we use it is because it works scientifically: it produces highly accurate, meaningful and predictive results in our laws, theories, and models, and more importantly alternative perspectives do NOT. So, there it is. --Jayron 32 11:10, 2 November 2017 (UTC)[reply]

These are great responses to my questions -- thank you all so much for taking the time to share the information and references you provided! 128.229.4.2 (talk) 12:37, 2 November 2017 (UTC)[reply]

November 2

What led to the increase in prevalence of breastfeeding?

According to this, https://en.wikipedia.org/wiki/History_and_culture_of_breastfeeding starting in the 1960s there was a resurgence in breastfeeding in United States and Canada.What caused the resurgence? — Preceding unsigned comment added by 2001:569:7733:AD00:AD6F:C935:4788:3388 (talk) 07:54, 2 November 2017 (UTC)[reply]

This paper, which was the first result when I typed "cause of resurgence of breastfeeding" into google, as seen here looks to have a good start to you research, as it not only has a wealth of information on its own, itself links to dozens of other studies on the matter. --Jayron 32 10:51, 2 November 2017 (UTC)[reply]

The OPs cited article notes that "By the 1950s, the predominant attitude to breastfeeding was that it was something practiced by the uneducated and those of lower classes. The practice was considered old-fashioned and "a little disgusting" for those who could not afford Infant formula and discouraged by medical practitioners and media of the time. By the 1960s the touted suitability of infant formula as a substitute for human milk was being questioned, which lead later to warnings such as "lack of breastfeeding—and especially lack of exclusive breastfeeding during the first half-year of life—are important risk factors for infant and childhood morbidity and mortality" (WHO 2003) and "a formula-fed child living in unclean conditions is between 6 and 25 times more likely to die of diarrhea and four times more likely to die of pneumonia than a breastfed child." (UNICEF 2007). Blooteuth (talk) 14:20, 2 November 2017 (UTC)[reply]

November 3

Tesla coils

Can Tesla coils be used as weapons on the battlefield, and if so, are there real-life examples of this (either in development or actually deployed)? 2601:646:8E01:7E0B:B9F4:7CD7:EC0A:69F7 (talk) 04:22, 3 November 2017 (UTC)[reply]

No, and no. Edison (talk) 05:48, 3 November 2017 (UTC)[reply]

Regarding the first question, why not? 2601:646:8E01:7E0B:B9F4:7CD7:EC0A:69F7 (talk) 06:26, 3 November 2017 (UTC)[reply]

Well, This dude actually built a portable, wearable Tesla coil gun, but it seems to lack any sort of real-world battlefield application, other than looking a bit scary. I'm quite certain that if it could be made into a usable weapon, somebody would have done it by now. Alansplodge (talk) 10:51, 3 November 2017 (UTC)[reply]

Slapping with a haddock could be used as a weapon, but the real question is whether it would be effective. A Tesla coil is fragile, power hungry and not terribly damaging. The best defence against them is some sort of tin hat or tin box to sit in, both of which are widely used by the opposing forces.

Also a Tesla coil is largely omnidirectional, meaning that it acts in all directions (your troops too), wastes energy in being effective in a direction where your enemy isn't, and makes it susceptible to the inverse square law, so seriously range limited.

Any sort of battlefield directed energy weapon needs to be just that: directed. It needs to put its energy in one direction, towards the enemy and them alone. This may also reduce the inverse square law effect (but look at far field and Fraunhofer beam for why lasers don't work how you probably think). Andy Dingley (talk) 10:56, 3 November 2017 (UTC)[reply]

Would that make this a war crime then? --Jayron 32 13:39, 3 November 2017 (UTC)[reply]

No, but it might be tench warfare. Andy Dingley (talk) 18:41, 3 November 2017 (UTC)[reply]

Are we allowed to give military advice? What happens if someone loses a whole war because of reliance on it? Will they sue the Foundation? --Trovatore (talk) 19:02, 3 November 2017 (UTC) [reply]

Don't worry about them. The Mule will eventually mess up their work. All roads lead to Trantor and that's where all stars end. --Jayron 32 02:51, 4 November 2017 (UTC)[reply]

I should point out that railguns have military application. However, those use pulsed DC rather than alternating current, which excludes them technically and spiritually from all things Tesla. Wnt (talk) 19:09, 3 November 2017 (UTC)[reply]

Technical Problem

Has any body noticed that it is just not possible to download the first pic in article Railgun in it's highest resolution? Why is it so ? RF regulars are kindly requested to pass it on to the appropriate Wikipedia people if it's a technical bug (as I don't know how to reach them, please) 124.253.7.215 (talk) 21:23, 3 November 2017 (UTC)[reply]

File:Railgun usnavy 2008.jpg worked for me just now, both via the "Original file" link on the image description page and via the "Download original file" item after clicking the download link in the media-viewer mode. Firefox-56.0.2. How exactly are you trying it? DMacks (talk) 21:34, 3 November 2017 (UTC)[reply]

Enabling works for new railway lines

Do enabling works for brand new railway lines such as demolition, utility and infrastructure diversions etc fall under railway civil engineering? Some people argue that it’s not railway civil engineering and is just general civil engineering. Clover345 (talk) 11:35, 3 November 2017 (UTC)[reply]

Civil engineering is a widely-recognized (perhaps the most widely-recognized) major engineering discipline. "Railway civil engineering" is not, though it seems like a useful subset or sub-discipline. As such, virtually everything that might plausibly fall under "railway civil engineering" will also fall under the banner of civil engineering (whether prefaced with "general" or not). — Lomn 13:28, 3 November 2017 (UTC)[reply]

General civil engineering. For example, if a major water line needs to be moved it doesn't really need a railway civil engineer. A cantilever rail bridge (with a speed rating of x) spanning a gorge is a different story. 196.213.35.146 (talk) 13:30, 3 November 2017 (UTC)[reply]

I wouldn't hire a railway engineering firm to design and build a bridge (and I probably wouldn't go to an advertising "general" firm, either). I'd go to a firm that does bridges. Which, I think, illustrates nicely that the proposed division isn't universal or clean. An engineer with rail specialization would need to provide input on either the water line or the bridge (What's the maximum weight on the line? How deep does the line construction itself go? What's the maximum grade permissible on or near the bridge? What about turning radius?) but likely would not have the specialist knowledge to design either the water line or the bridge itself. Conversely, the engineer responsible for either of those projects would likely not have the specialist knowledge to derive the rail-applicable requirements that impact the designs (or for a great many other requirements). Engineering work of any substantial magnitude is not a single-subdiscipline affair. — Lomn 14:18, 3 November 2017 (UTC)[reply]

(ec) In part, the answer probably depends on why you're asking—there may be jurisdiction-specific situations that have explicit legal/regulatory definitions and requirements as to what constitutes "railway" civil engineering. One might also be taking a university course where the instructor has a particular and specific definition in mind. The question could come up in dealing with a professional organization that has particular requirements for membership.

The first relevant Google hit I get is for the UK's Railway Civil Engineer's Association, which says "Railway engineering is an engineering discipline that deals with the design, construction and operation of railway systems." For membership, their criteria include:

"Those who are engaged in, or been engaged in, the development, design, construction or maintenance of engineering infrastructure for railway operations. Ordinary members will normally be professional engineers. ..."

There's some wiggle room there, but I would tend to interpret those in a manner akin to that suggested by 196.213 above. A railway engineer would determine the location and design of the new line, and would likely be involved in identifying required demolition projects and utility relocations. Once those requirements were specified, however, it would not necessarily require railway-specific knowledge or training to carry them out; they're not railway engineering. If a sewer pipe needs to be relocated to allow the construction of bridge footings, it doesn't matter if the bride is for road or rail use—the pipe just needs to be somewhere else.

Indeed, substantial demolition or utility relocation projects would likely require their own flavors of engineering experts, with specific training and qualifications that a railway engineer wouldn't be expected to have and wouldn't be permitted to sign off on. On a major project, I would expect multiple different types of engineers to collaborate. And I am sure that there are some blurry edges associated with some tasks, as well. Honestly, your best bet might well be to contact organizations like the RCEA directly, and just ask them how they handle this question. TenOfAllTrades(talk) 14:39, 3 November 2017 (UTC)[reply]

Interesting. But surely there are some significant differences between a railway bridge and a road bridge as they will be subject to different types of loading. Clover345 (talk) 14:47, 3 November 2017 (UTC)[reply]

See [45]. This [46] shows how the two disciplines interact. At Upper Holloway, for example, the bridge carrying the main road from London to the north had to be reconstructed and various utilities relocated. 80.5.88.70 (talk) 15:47, 3 November 2017 (UTC)[reply]

Yes, there can be significant differences also in aesthetics, budget and whether there is a pre-existing foundation. The article Bridge gives an introduction to the many options available to the project engineer who needs to have expertise about the failures of bridges that first assumed national interest during the Victorian era when many new designs were being built, often using new materials. Blooteuth (talk) 16:53, 3 November 2017 (UTC)[reply]

Is it more common to classify civil engineers as infrastructure civil engineers or buildings civil engineers? Clover345 (talk) 17:47, 3 November 2017 (UTC)[reply]

Here are current examples of recruiters for both Civil Infrastructure Engineer and Buildings – Civil Engineer. Blooteuth (talk) 19:04, 3 November 2017 (UTC)[reply]

X-rays

1.As we know that most typical digital cameras (likes the ones in smartphones etc.), are able to detect infrared rays, unlike human eyes are (except in very rare cases). Are these typical digital cameras like the ones in our mobiles, or our DSLRs etc. also able to catch X-rays (let's, for sake of simplicity, limit the question to the X-rays that are produced by the machines used to look into the human-body in medical diagnosis works).

2. I have read somewhere that if the simple task of detaching the adhesive cellophane tape from it's roll, is done in strong vaccum, X-rays are produced ! Is that a fact or a myth ? Jon Ascton (talk) 20:10, 3 November 2017 (UTC)[reply]

Theoretically hard X-rays hitting a CCD will cause flashes of light, which can be detected. However the camera optics does not work for X-rays. So, X-rays coming from any direction will be detected - the camera will not display any X-ray image. Ruslik_Zero 20:26, 3 November 2017 (UTC)[reply]

The scotch-tape thing is real. here are researchers from UCLA actually imaging someone's finger bones this way! ApLundell (talk) 21:01, 3 November 2017 (UTC)[reply]

this article suggests that a ccd from an ordinary digital camera would be a poor way to detect gamma rays, but this article talks about an East Hartford company that proves it can be done, at least if the source is dangerously powerful. Neither are these are about the precise frequency of gamma waves that make up medical x-rays, but they may be close enough for your purpose. Ruslik0 is correct that in both cases, since x-rays will pass straight through the optics (and everything else), you won't get an image as much as you'll get random static. ApLundell (talk) 21:22, 3 November 2017 (UTC)[reply]

Related : If you've ever watched any of the videos coming from the space station, you'll know that all their DSLRs have bad pixels. Gamma Rays.

ApLundell (talk) 21:23, 3 November 2017 (UTC)[reply]

The semiconductor elements of the CCD array are affected by X-rays, so they will "detect" them as in the above responses. However, all of the rest of the semiconductor elements in the camera are also affected by X-rays at least to some extent, so enough X-rays to register on the CCD as a bloom may also be enough X-rays to produce a soft error while the camera tries to process the image, resulting in anything from a tiny glitch, to loss of the image, to a latch-up requiring the camera to be powered off and back on. A very large dose of X-rays can result in damage rendering the camera unusable.-Arch dude (talk) 23:15, 3 November 2017 (UTC)[reply]

There are a few phone apps that use the builtin CCD camera as a gamma/x-ray detector.[47] DMacks (talk) 18:53, 4 November 2017 (UTC)[reply]

Namibia "hammocks"

The article on Namibia says "Near the coast there are areas where the dunes are vegetated with hammocks", linking hammock (ecology). The source linked to [48] currently consists of the words "index.php". The article on hammocks lists a number of different things in Florida -- there are xeric hammocks [49], but these are wet, surrounded by well-drained sandy soil. By contrast, the article on Namibia describes the entire country as arid or semi-arid. Stupid searches get nothing but photos of tourists, obviously; "xeric hammocks" and Namibia turns up nothing much. Your mission: figure out if there are really (ecological) hammocks in Namibia, what kind they are, whether they are in some special foggy microclimate that is not arid so that it is actually too wet around them for trees like in Florida. Wnt (talk) 23:12, 3 November 2017 (UTC)[reply]

The coast of Namibia is known for its significantly different climate to inland. The Atlantic coast of Southern Africa has much colder currents than the Indian Ocean coast and this leads to the famous cold fogs of coastal Namibia. Although these lead to some rainfall, notable itself in this largely arid climate, they also produce significant precipitation as dew on plots of coastal vegetation. So the vegetated plots (whatever they're called, I'm unfamiliar with hammocks) become self-sustaining. Andy Dingley (talk) 23:41, 3 November 2017 (UTC)[reply]

Thanks to the Wayback Machine, Here's that source article as it appeared in March 2016. The word "hammock" does not appear, but "hummock" does (and the article hammock (ecology) suggests that the one derives from the other). The relevant sentence is "Vegetated dune-hummock areas are common near the coast", but I don't know if it's correct to interpret that as meaning hammocks. --69.159.60.147 (talk) 04:44, 4 November 2017 (UTC)[reply]

The distinction between a hummock and a hammock is subtle. One is an slightly elevated coastal area with woody vegetation. The other is a high mound near the sea with trees. Most importantly for our discussion, one has a "u" in it, while of absolute importance to settling the dispute, the other has an "a". As to which applies to the coast of Namibia, I'm not entirely sure. Perhaps choosing a third term which is more universal may be useful. --Jayron 32 04:59, 4 November 2017 (UTC)[reply]

... and etymologists seem unclear and not in agreement about whether or not one word was derived from the other in the sixteenth century. I agree that choosing a more world-wide term would be more appropriate for this area and this article. Dbfirs 08:43, 4 November 2017 (UTC)[reply]

The "dune-hummock" tip is highly informative -- dune hummocks = nabkhas are well known in coastal areas around the world; their anchoring by bushes in Finland is described, for example. [50] There are a number of single hummocks visible as images, though this photo suggests the hummocks can be densely packed in larger areas. This link suggests a more specific location and suggests the mist is salty. There is a lot of information about Namibian dunes overall [51] but I'm still a bit unclear whether the dune-hummocks are classified in any higher-level unit than the single little hump. Wnt (talk) 11:40, 4 November 2017 (UTC)[reply]

Hey User:Wnt, I'm confused about what you're unclear on. Out side of the slightly more specific sense described in our article, hammocks are generally just raised bits of vegetation; often there is some interesting process that forms them. I don't think there's anything intrinsic/necessary about moisture, but often they have something distinct going on ecologically, behaving as relatively isolated communities, often centered around a few sort of ecosystem engineer species that provide refugia or food etc. I am not terribly familiar with hammocks in Namibia, but e.g. here [52] they are clearly referred to as hammocks, though I can't figure out what they mean by "nama plants", except that I'm pretty sure it's not nama_(plant), as that is a new world genus. I think it might be a garbling of the plant called "!Nara" in the Nama language, Acanthosicyos_horridus, which is endemic to Namibia and provides a mechanism for dune/hammock building as described here [53]. Sometimes, when speaking of hammocks, the word can mean either one specific hammock, but it can also be used to stand for the set of all of them in the region. E.g. "a hammock species", or "the hammock [ecology/community/system]." Does that help at all? SemanticMantis (talk) 19:05, 4 November 2017 (UTC)[reply]

@SemanticMantis: Our article describes the hammocks as stands of trees, while the dune hummocks I was looking at in our other article are individual bushes anchoring a mound a few meters in size. The source you cited is useful - I ran down its source at a doctoral thesis online [54] which says "The characteristic plant at the study site is Acanthosicyos horridus, the nara, a member of the Cucurbitaceae, and an endemic of the Namib sand dunes. The species grows in the dune valleys were there is access to underground water." The thesis uses the word "nara" a bazillion times, so indeed the other source was in error. Crucially, it explains (p. 16) that "Nara plants form dense, tangled bushes and as sand is trapped underneath the branches, a hummock reaching considerable size is built up. These hummocks can reach sizes up to 4m in height and cover an area of up to 1000 m2, forming micro-ecosystems within the dunes of the Namib Desert." So bushes not trees, centered on underground water rather than avoiding it, but also a large formation; I'm not sure now which is larger. In short, although you weren't sure how I was unsure, you led me to the exact thing to explain what I was unsure about. ;) Now I just have to figure how to bring this back to the article. Wnt (talk) 23:20, 4 November 2017 (UTC)[reply]

November 4

Star in Cancer named for Marina Popovich

Marina Popovich says that a star in Cancer is named after her, but the reference is in Russian and it doesn't come up for me. Which star is it? (List of stars in Cancer doesn't list those types of names.) Bubba73 ^{You talkin' to me?} 05:24, 4 November 2017 (UTC)[reply]

Very few stars are officially named after individuals. See IAU Working Group on Star Names, and note that the lists linked from that article's references do not include the names "marina" or "popovich". So this seems unlikely. (Note, there are companies that sell the right to "name" a star but nobody else recognizes those names. See Stellar designation#Sale of star names by non-scientific entities.) --69.159.60.147 (talk) 09:18, 4 November 2017 (UTC)[reply]

Cancer is her Sun sign (90 to 120 degrees ecliptic longitude). Sun in International Astronomical Union Cancer after 8:41pm UTC+3. Sagittarian Milky Way (talk) 12:57, 4 November 2017 (UTC)[reply]

That reference is dead. Ruslik_Zero 20:39, 4 November 2017 (UTC)[reply]

This here says it's Alpha Cancri (last para), and it was Gherman Titov who gifted her the certificate to the effect. However, as has been noted, unlike comets, say, stars are never officially named after people, not that it keeps shady companies from selling the stuff. 78.53.24.148 (talk) 21:21, 4 November 2017 (UTC)[reply]

That's what I was going to say, but then I looked at the references (cited above). Very few stars are officially named after individuals, but "never" is now wrong. The longstanding nickname Barnard's Star is now an official name, for example. --69.159.60.147 (talk) 04:24, 5 November 2017 (UTC)[reply]

Thanks, I thought that it probably wansn't official. Bubba73 ^{You talkin' to me?} 02:42, 5 November 2017 (UTC)[reply]

Resolved

(Simply because it hasn't been linked yet) Stars named after people does list a few more besides Barnard's Star. Some, such as 61 Cygni aka 'Bessel's Star', do have different official names, but there are other examples (e.g. Kapteyn's Star). Marina Popovich is not on that list, nor is she mentioned in the subsection "Covertly named stars". ---Sluzzelin talk 05:28, 5 November 2017 (UTC)[reply]

Most comets are named after people, and so are some asteroids 45 Eugenia. 86.155.148.59 (talk) 16:00, 5 November 2017 (UTC)[reply]

Stars with naked eye

I couldn't figure out how to word it properly with Google but my question is: I see a lot of amazing pictures of galaxies and stars and cosmic dust and all that, but how much of that is actually visible to the naked eye? I am planning to take a trip to a place with little to no light pollution and I'm trying to temper my expectations. Thank you! — Preceding unsigned comment added by 80.6.102.227 (talk) 22:21, 4 November 2017 (UTC)[reply]

See Bortle scale for examples of astronomical objects visible with the naked eye at various levels of light pollution. The Naked eye article may also be useful. Tevildo (talk) 22:28, 4 November 2017 (UTC)[reply]

As Bortle himself explains here, you need to get quite far away from big cities, light reflects back from the atmosphere, making the sky even 100 km away from a city become very slightly gray. While you can then see many faint stars, nebulae with low surface brightness will still be drowned out. E.g. in Western Europe, you won't be able to easily see the Triangulum Galaxy with the naked eye, it may be possible to see with a lot of effort from the Alps. This is because it's hardly possible to get away more than a few hundred km from a large city like London, Paris, Brussels, Berlin etc. etc. in Western Europe. Ideally you need to be 1000 km away from such big cities, then you should be able to easily spot such faint objects like the Triangulum Galaxy. It is from such places where you can spot even fainter object with effort, e.g. the astronomer Brian A. Skiff has seen the galaxy M 81 with the naked eye as he mentions here. But he failed to spot Neptune with the naked eye, even though it is theoretically possible to do so. Count Iblis (talk) 00:34, 5 November 2017 (UTC)[reply]

The less lightpollution the better ofcourse but actually the weather is much more important since without a clear sky, without any lightpollution, you would only have a "lightunpolluted" view on the clouds. --Kharon (talk) 01:59, 5 November 2017 (UTC)[reply]

You don't need 1,000 kilometers. Maybe in space or in an airplane when you can see further but from sea level look at the light pollution map of the ocean near New York or Tokyo. If you need 1,000 kilometers somewhere it's because of closer cities, suburbs or farms, not because of your city (also light fishing and human and natural fires can cause enough light to cause light pollution. I haven't done the math to see if there's enough air in the volume lit enough by a candle for things that small to cause it too but if it could it'd only have inches or feet of range. You'd also have to avoid seeing the candle or anything lit brightly by it for 30 minutes to adapt your eyes to the dark before you could test this. [You can look at a candle from less than 1,000 feet away without affecting your dark adaption] so it's got to be much closer if the air around that light is glowing enough from scattering to affect the view) Sagittarian Milky Way (talk) 05:52, 5 November 2017 (UTC)[reply]

Photographs of the less bright astronomical objects usually show too little (especially film without a bulb setting) or too much (i.e. taken in space, infrared, composites of long exposures, sometimes including black and white frames through a filter that blocks all but the tiny fraction of the rainbow nebulae glow in (which are then colored i.e. hydrogen red in software, nebulae can be seen with the naked eye but they're gray and usually smaller)) Infrared's pretty neat. The naked eye Milky Way looks brighter the closer to the center it is (both centerline and center point) except a rift of dust seems to block what would be some bright-ass stuff. And it is, Milky Way dust is amazing. 1,000 light years doesn't dim much but 50,000 light years towards the far side of the galaxy dims 100,000,000,000,000,000,000 times. The redder the light or infrared the picture is taken in the further into this dust you can see. Also most stars are brighter in infrared than any color of light. There's a star barely visible to the naked eye that's the 3rd brightest star in the sky in near-infrared. It's a class above Sirius in any color of light but it's just too red for humans. Sagittarian Milky Way (talk) 05:34, 5 November 2017 (UTC)[reply]

The user geolocates to Dunstable, UK. In New Jersey one can go to the New Jersey Pine Barrens, Batsto, New Jersey being a good place to stop right off the road in a public field, and see the Milky Way and a very bright starry sky on clear, moonless nights. But in the Northern Hemisphere galaxies appear at best as star-sized nebulae to the naked eye. The Andromeda Galaxy, the closest non-dwarf galaxy to ours is in the Southern Hemisphere. μηδείς (talk) 02:30, 5 November 2017 (UTC)[reply]

That location isn't too similar to what the darkest possible looks like really. It's only dark by New Jersey and Philly area standards. The closest land you can't detect light pollution with the naked eye from if you know what to look for might be Canada. Sagittarian Milky Way (talk) 04:08, 5 November 2017 (UTC)[reply]

Ah, do you want to check that? I think you might have your chart upside down. The Andromeda Galaxy – with a declination of +41° is very much visible in the northern hemisphere, and most easily viewed from there. For southern observers, Andromeda never gets very far from the northern horizon. The Magellanic Clouds are presumably the dwarf galaxies you're thinking of, and they're both around -70° declination, deep in the southern sky. TenOfAllTrades(talk) 03:16, 5 November 2017 (UTC)[reply]

You're right, I was thinking Magellanic Clouds. Stupid me. In any case, you still need visual aids to make out anything other than a fuzzy star. Where I live, you are lucky to see Orion, Sirius and the Pleiades in the right season, and perhaps the Big Dipper. μηδείς (talk) 03:39, 5 November 2017 (UTC)[reply]

The Large Magellanic Cloud isn't small to the naked eye. And the Milky Way doesn't look too dissimilar to astrophotographs of spiral galaxies edge-on and is a bit more than a fuzzy star (360 degrees wide). Sagittarian Milky Way (talk) 04:08, 5 November 2017 (UTC)[reply]

I did some searching on this question a while ago while writing a trivia-league question. Pretty much every source I checked made different assumptions and gave different numbers, but the consensus was clearly that under ideal naked-eye conditions on the Earth the number of stars you can see as individual objects at one time is a few thousand. The question is whether you can see stars of magnitude 6 or brighter, or 6.5 or brighter, or whatever; also, stars near the horizon are dimmed and you won't be able to see all of them that you could if they were higher. Anyway, I downloaded the Bright Star Catalog, which was available somewhere under here, and found 5,080 stars listed of magnitude 6 or brighter; 8,404 of magnitude 6.5 or brighter. Of course at any particular time and place about half of them will be below the horizon. So it's pretty safe to assume 2,000-plus; 3,000-plus, maybe not. --69.159.60.147 (talk) 04:36, 5 November 2017 (UTC)[reply]

The sky with the most individually distinguishable naked eye stars probably has the Milky Way near the zenith. The winter sky has more bright stars cause of the Orion Arm which we're in (but closer to the inner edge), the summer sky has more dim stars cause the Orion Arm's a minor spur of the Persus or something arm and the next arm in (Scorpius-Sagittarius?) is major but further (as one would expect from us being in a minor inner spur of the next outer major arm). The Southern spring sky probably has more individually resolved stars than the Northern fall and you could still see some of the midnorthern summer and winter stars when Centaurus or Crux is overhead so it's probably not when the Cepheus or Cassiopeia Milky Way is high. Sagittarian Milky Way (talk) 05:32, 5 November 2017 (UTC)[reply]

See Dark-sky preserve. There is an organisation which inspects areas and grades them [55]. 86.155.148.59 (talk) 15:22, 5 November 2017 (UTC)[reply]

As an aside, here's a link to a worldwide light pollution survey, presented as an overlay on Google Maps: link. (Sadly, I live in one of those big-city white areas at the ugly end of the Bortle scale.) The map is based on 2006 data, but most areas won't have changed much beyond a gradual worsening. TenOfAllTrades(talk) 15:26, 5 November 2017 (UTC)[reply]

I do wonder if we're taking the question in a bit of the wrong way. Counting stars and spotting Triangulum are certainly ways to assess viewing conditions, but I get the impression that the OP is perhaps at least as interested in a more qualitative description, with particular emphasis on similarities and differences between what you see with the naked aye versus photographs. Correct me if I'm mistaken, but I presume that the OP is new to dark-sky observing (and probably has fairly limited observing experience in general—welcome to the hobby!); learning to find the most obscure and difficult-to-see objects probably isn't the priority here. So what are the differences that will stand out?

A lot more stars. With the naked dark-adapted eye, good seeing (that is, good atmospheric conditions), clear skies, unobstructed view to the horizons, and (this is important) no Moon, you're looking at somewhere over 4000 stars at magnitude 6.5 or brighter: [56]. This compares quite favorably with the few dozen you might see from a city location, or the few hundred you might get at a suburban site.
But not all the stars. Telescopes, binoculars, even regular camera lenses all capture light through a front aperture bigger than the pupil of your eye, and so they collect a lot more light to play with. (This page shows the difference between a 200 mm medium-sized amateur telescope and the human eye in the first figure.) Film or digital camera sensors can collect that light over an extended period of time, too (several seconds, minutes, or even hours), to pull even the faintest objects out of the background. I know from experience that if I put my very average consumer-grade DSLR on a tripod outside with a good-but-not-stellar (ahem) medium-angle lens, I can shoot a five-second exposure that easily displays stars that are fainter than 9th magnitude—even from a badly-light-polluted city location.
Less color than you might expect. Color vision just isn't very sensitive. Most stars, even under ideal conditions, look plain white; a few of the brightest ones have visible color: [57]. Similarly, the small number of naked-eye nebula (like the Orion Nebula) are smudges of gray, not sprays of violet: [58].
Lower magnification and resolution. Globular clusters are smudges rather than dense piles of pinpoint stars. Most of the objects in the sky won't show structure or detail to the naked eye, just smudges and single points. Remember that the list of Messier objects was compiled by a frustrated naked-eye comet-hunting astronomer who wanted a catalog of all the little fuzzy smudgy things in the night sky that looked like they might be comets—but weren't. (Amateur astronomers refer to faint nebulae and distant galaxies – somewhat tongue in cheek – as 'faint fuzzies'.) For a few extended objects, you may only be able to see the brightest parts with the naked eye. For example, the Andromeda Galaxy is nearly three degrees wide (the full Moon is only about half a degree across) but you'll only be able to see a wee smudge in the middle with the naked eye.

All that said, don't get the impression that it's not worth looking at the night sky with the naked eye. It's magical. The sky feels close enough to touch. The Milky Way is awesome. Be patient and let your eyes get fully dark adapted. Do not look at your smartphone. Lie down on your back and soak it in. TenOfAllTrades(talk) 15:26, 5 November 2017 (UTC)[reply]

Using food or money on research participants

When “animals” are used in research experiments, they are rewarded food. When humans are compensated for their time, they are given money. Is this just a widespread assumption by the researcher, or are humans really attracted to money over food? If a researcher has a low budget, then will offering a piece of fruit work instead of giving money? Or do researchers still have to allot some of the budget to paying the participants? 50.4.236.254 (talk) 23:55, 4 November 2017 (UTC)[reply]

The articles Human subject research and Animal testing give some perspective on these kinds of research, both of which are normally guided by ethical restraints, see ref. 1 and ref.2 respectively. Financial or food incentives may form part of the research methodology, or merely be necessary outlays to obtain participants. Blooteuth (talk) 01:20, 5 November 2017 (UTC)[reply]

(ec) There are some questionable assumptions there about how humans are compensated for their participation in research. Over the last few decades, I have received:

A smidgen of course credit (in an undergraduate introductory psychology course) for participation as a subject in psych experiments;
A chocolate chip muffin in exchange for a vial of blood (while a grad student) for a neighboring bio lab that needed a 'normal' control;
Nothing whatsoever in exchange for consent to carry out research using biopsy specimens collected in the normal course of a surgical procedure I underwent;
A small-but-not-negligible cash payment (enough for dinner and a pint at the local pub) for participating in a series of telephone surveys tracking my recovery from the surgery mentioned in the previous bullet.

In my very tiny sample of experience, research participation has seldom resulted in a cash payment, and food has been used as a perfectly acceptable reward.

More generally, there are serious ethical concerns around cash payments to research subjects. Research ethics boards (REBs) and regulatory agencies (like the FDA) tend to frown on studies that propose using overly-large payments to influence subjects and induce consent or agreement to participate in studies against their better judgement. These guidelines from UC Berkeley touch on a number of principles, and highlight the potential for undue influence or coercion. These guidelines from the University of Toronto draw a distinction between reimbursement (repayment for out-of-pocket expenses like transportation and parking) and compensation (payment – monetary or otherwise – for the participant's time and effort).

On the question of whether and how various rewards work, here's a quote from a relevant paper.

"However, empirical evidence demonstrating that payment is necessary and/or effective for the recruitment of clinical research subjects is limited. People appear to be attracted to research and motivated to participate for a variety of reasons. Healthy volunteers, who are frequently paid and unlikely to benefit medically from research participation, are often attracted to research and motivated to participate by money. Yet they appear to have a variety of other motives besides those of a financial nature for participation in research, including curiosity, altruism, sensation seeking, and desire for attention provided by physicians (24–26). Patient-subjects — those who suffer the disease or condition under study in a particular research protocol — are often motivated to participate by the hope of personal therapeutic benefit. When patient-subjects enroll in clinical studies and they understand the likelihood of direct medical benefit to be remote or nonexistent, their motivations are likely to be similar to those of healthy volunteers. Although patient-subjects are often offered payment for their participation in clinical studies, little research has been done to evaluate the extent to which money influences recruitment or their willingness to participate (21). Given the diverse motivations of subjects in clinical research and a lack of relevant data, it is difficult to know how much paying subjects helps to accomplish recruitment goals."

The short version is that different people are motivated by different things, and study participants often receive trivial compensation. TenOfAllTrades(talk) 01:39, 5 November 2017 (UTC)[reply]

The question is confusing "reward" as part of a research protocol itself (training a behavior, etc.) with "compensation" for being a participant. You don't need to pay mice, you just pay a breeder and then drop them in your maze. Token rewards involved in protocols depend on what behavior is intended to be learned. DMacks (talk) 01:49, 5 November 2017 (UTC)[reply]

From what I gather by talking with my fellow clinical trial participants, while some do it out of charity, they still need to take unpaid leave to participate, still other participated to raise funds while on an OE. I was one of the former, and I would be rather irked if I weren't comensated for my lost earnings. I already sacrificed my time, and it's exhausting being poked and prodded at all hours of the day and night. Offering me fruit instead of money would be an insult, I'd rather take nothing in compensation. Plasmic Physics (talk) 05:21, 5 November 2017 (UTC)[reply]

It's purely a matter of convenience. Animals would be given money too if only they could be persuaded to work for it. Looie496 (talk) 13:58, 5 November 2017 (UTC)[reply]

Volunteers may only eat what they are given (if they smuggle in food they may be discharged and/or not paid).[59] This is because diet affects how the body metabolises the trial drug. 86.155.148.59 (talk) 15:39, 5 November 2017 (UTC)[reply]

November 5

Burqan 2 ballistic missile spesifications?

All over the news today is the claim that Saudi Arabia shoot down a Burqan 2 ballistic launced from Yemen. I have looked, but fail to find much of anything about the Burqan missile; who made/makes it, spesfication, design lineage, anything. Do anyone have any pointers or know of any resources on this missile? WegianWarrior (talk) 11:12, 5 November 2017 (UTC)[reply]

See Volcano H2 for our article. Perhaps some redirects need to be created. Tevildo (talk) 12:04, 5 November 2017 (UTC)[reply]

Thank you :) WegianWarrior (talk) 16:45, 5 November 2017 (UTC)[reply]

Deodorant Manufacturing Process

How does a Deoderant remove foul odors? Is it activated Carbon which is used to absorb foul odors? — Preceding unsigned comment added by 117.194.220.156 (talk) 13:40, 5 November 2017 (UTC)[reply]

I think our deodorant article explains it in a reasonably clear way. Looie496 (talk) 13:56, 5 November 2017 (UTC)[reply]

Are you referring to body deodorants? Here is an article talking about how body deodorants work. Also see body odor. Bus stop (talk) 13:57, 5 November 2017 (UTC)[reply]

Personal anti-perspirants work by applying an astringent to the skin pores, thus reducing perspiration. Most body odour develops from bacterial action on stale perspiration. These are usually aluminium based, often based on alum (a common one in some countries is just rubbing an alum block over the skin). In the West, "aluminium free" anti-perspirants are sold by fashionable fools and charlatans when these are made from alum (which of course, contains aluminium).

Deodorants for personal use are mostly perfumes which camouflage odours, although often include anti-perspirants and some include biocides to try and reduce the skin bacteria. Some, like Lynx (UK) / Axe (US) are so powerful and generally unpleasant that they have become known as the smell of male teenagers. The phrase "Glasgow shower" (other despised neighbouring towns are available) refers to the practice of never washing, but merely spraying on another layer of artificial smell. Trying to remove skin bacteria is often not a good strategy: skin will have a colony of some bacteria, and removing the benign ones may encourage a worse group to predominate. Also the usual problem of antibacterial resistance can develop.

For cleaning fabrics, adsorbants are used, and have been used since ancient times. They aren't used on the body as they'd leave dust behind. Activated carbon isn't used on fabrics, because it would leave ingrained black dust behind, but fuller's earth is. A modern and more powerful version of this are the odour eliminators such as Febreze which are based on cyclodextrin molecules.Andy Dingley (talk) 14:32, 5 November 2017 (UTC)[reply]

Most Deoderant's simply use Salt to "paint" a zone with it which makes it inhospitable for the bacteria which naturally thrive on your sweat and dead skin cells and thereby produce the smell as waste product. So deodorants dont remove smell, they try to prevent it. Also deodorants often additionally contain perfume to make customers happy and secure of themselves. So you can make your own deodorant for a few pennies instead of buying the very expensive salt-based "beauty products"! Go try! --Kharon (talk) 14:48, 5 November 2017 (UTC)[reply]

What do you mean by "salt" here? Common table salt, sodium chloride? In which case, no they don't. Andy Dingley (talk) 15:00, 5 November 2017 (UTC)[reply]

Note that the correct spelling is deodorant. It's misspelled by two editors above. Akld guy (talk) 15:50, 5 November 2017 (UTC)[reply]

@@ Line 376: / Line 376: @@
 :''(Simply because it hasn't been linked yet)'' [[Stars named after people]] does list a few more besides Barnard's Star. Some, such as [[61 Cygni|61 Cygni aka 'Bessel's Star']], do have different official names, but there are other examples (e.g. [[Kapteyn's Star]]). Marina Popovich is not on that list, nor is she mentioned in the subsection [[Stars_named_after_people#Covertly_named_stars|"Covertly named stars"]]. ---[[User:Sluzzelin|Sluzzelin]] [[User talk:Sluzzelin|<small>talk</small>]] 05:28, 5 November 2017 (UTC)
+::Most comets are named after people, and so are some asteroids [[45 Eugenia]]. [[Special:Contributions/86.155.148.59|86.155.148.59]] ([[User talk:86.155.148.59|talk]]) 16:00, 5 November 2017 (UTC)
 == Stars with naked eye ==