Wikipedia:Reference desk/Archives/Science/2020 August 7

= August 7 =

What can cause frequent tapping sounds from an inactive bathroom fan?
Sagittarian Milky Way (talk) 01:03, 7 August 2020 (UTC)


 * No doubt a multitude of things, maybe even wind from outside shaking some parts. You've ventured out of the realm of en-wiki with this question. Maybe look up Y!A. Zindor (talk) 03:42, 7 August 2020 (UTC)
 * Many of those fans have one-way slats on the outside that are designed to ensure that air can flow out but not in. On a windy day these can flap about.--Shantavira|feed me 09:54, 7 August 2020 (UTC)

If neutrinos have mass, how do they travel at the speed of light?
Example: SN 1987A neutrinos famously reached observers several hours before the visible light arrived, over a distance of 170,000 LY. That's because they made their way through the supernova mass without obstruction, while the light took longer to make its way through. But, what about special relativity? Would they experience mass dilation? Various figured like 0.3 eV are given for the neutrino mass but it's not clear whether that's a rest mass (if neutrinos even have that), or that neutrinos are always travelling at lightspeed and that's their relativistic mass. Thanks. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 03:00, 7 August 2020 (UTC
 * If one were to assume that neutrinos travel at the speed of light, then i can see only two possibilities: either the special relativity theory needs updating, or neutrinos possess infinite energy. The Measurements of neutrino speed article might contain the answer you are after, and is more reliable than my ramblings. Zindor (talk) 04:02, 7 August 2020 (UTC)


 * If they do have mass, it is very small, and they have a highly relativistic speed. Almost all their energy/mass is due to that mass dilation. You can consider refractive index as something that slows down light. I do not know if there is an equivalent thing for neutrinos, however they do have a very small interaction with normal matter by way of the weak force. Graeme Bartlett (talk) 04:11, 7 August 2020 (UTC)


 * Thanks all.  Measurements of neutrino speed  was very helpful. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 09:12, 7 August 2020 (UTC)
 * A lot of a supernova's light is produced by radioactive decay of stuff in the expanding cloud of ejecta, and that decay of course doesn't happen instantly. Off the top of my head I don't know the relative contributions of different things; you'll have to dig into some sources if you want precise numbers. The neutrinos, by contrast, are all produced in the initial core collapse, and actually are what most of the energy released in a supernova goes into. --47.146.63.87 (talk) 23:39, 8 August 2020 (UTC)

chemical vocabulary history
Is there a good book about the development of modern chemical nomenclature? —Tamfang (talk) 05:33, 7 August 2020 (UTC)


 * Any particular area of chemistry (chemical elements, organic structures, generic drug names, salts, strong acids, environmental substances, etc.)? DMacks (talk) 06:58, 7 August 2020 (UTC)


 * Like who came up with –ane and –ene and –yne, and when? —Tamfang (talk) 05:53, 8 August 2020 (UTC)


 * Wouldn't that be the "Gold" Book, or IUPAC Compendium of Chemical Terminology, which is almost surely lying around in one of your nearby labs or classrooms or libraries? Pretty much every single item contains either a source, a reference to another color book, or an original research citation.  The book is also available in PDF form at zero cost: but the really serious scientist probably wants to buy a copy.  (sic).  That's probably as close to a compendium dictionary of chemical etymology as you'll find... there are plenty of in-book citations to previous papers and conferences and older publications that itemize the development of individual terms.  Nimur (talk) 17:37, 7 August 2020 (UTC)


 * Oooh, a few excerpts I found exciting, extracted from the page on the lore of the Gold Book (which provides some fascinating meta-historiography on the topic of the development of the documentation of the documentation):
 * "The impact of the Gold Book on society is difficult to measure due to a lack of information of usage of the Gold Book website prior to 2017...  Data obtained for Wikipedia events (edits to pages where a DOI was added – all languages), indicates that Gold Book DOIs (each entry has a DOI) have been added for 1952 entries (~30% of current entries) as well as the overall Gold Book being referenced 2485 times...   Looking deeper these entries are referenced in 7581 Wikipedia pages across 84 countries."
 * Dear colleagues, ... today I can say I am proud of our efforts.
 * Nimur (talk) 17:44, 7 August 2020 (UTC)


 * A quick glance at that book did not turn up any etymology. —Tamfang (talk) 05:53, 8 August 2020 (UTC)
 * Sorry, it looks like I posted before you clarified that you were looking for information about those suffixes in particular,... but those aren't exactly "modern," are they?
 * For what it's worth, the Gold Book lists citations for alkane et al.: e.g. Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)...
 * Are you looking for "first use"? Because that would be, by way of tracing those citations onward and backward, ...:
 * August Wilhelm von Hofmann, grandfather of systematic chemical nomenclature, author of an Introduction to Modern Chemistry (1865), conveniently available in PDF form at zero cost and written in the English language by its polyglot author.
 * And, although it is a little bit "pre-modern" in its terminology, and although it was written a little early during the long march toward the theories we know today concerning the atom and the molecule, the book is mostly intelligible, highly methodical, and broadly accurate. The author provides, in Lecture VI, a thorough experimental chemical analysis of the Marsh Gas, which we know today as Grubengas  Fire-damp methane and several similarly-named impurities.  It is over the course of several more lectures that the author deduces names for specifying those impurities, using detailed chemical analysis and a whole lot of bad Latin and worse Greek, and he even writes a lovely etymology of the word "hypothesis," for the non-polyglot reader of English.  This is followed by more quantitative analysis of atomic valence, with several worked lab examples, and a lot more bad Latin and worse Greek and a few English words that are quite foreign to the modern reader ("criths" and "barleycorns" and "chemism" - though quite important to the historian of science!), and the inevitable experimental discovery of a "new and pregnant law of chemistry, - that of combination in multiple proportions."
 * To say the least, this book played an important role in the history of science at-large, and not only in its etymology.
 * IUPAC claims that this approach became standardized at the Geneva Conference of 1892, but I think any realistic historian will tell you that nomenclature-standardization was a long, gradual process that continues to this day.
 * ...if you go back farther than those time-periods, you get in to the messy soup of protoscientific alchemical chemistry. The old names for simple chemicals - like methane and methanol - get ultra-confusing, because pre-scientific (e.g. pre-19-th-century) attempts to isolate those chemicals weren't very good or methodological.  So the names they use aren't necessarily naming the right chemicals... and the names they applied were not particularly systematic, which is why you have synonyms like methylene and methanol that may-or-may-not refer to the same thing (and if you're reading very old literature, you can't safely assume these terms mean what you think they mean).
 * If you read works by the greats, like Michael Faraday, you have to use a lot of modern judgement to decide exactly which chemical you think he's talking about, based on the properties he describes. And if you go back much farther than that, you need to start learning alchemical and astrological codes, because the old authors intentionally obfuscated their secret recipes using symbology and misdirection.
 * Nimur (talk) 17:13, 10 August 2020 (UTC)


 * Don't forget to consult our sister project Wiktionary -ane, -ene, -yne. Some of us try to add chemistry words there. The when aspect is missing from these however. Graeme Bartlett (talk) 06:24, 8 August 2020 (UTC)

To clarify. I'm not looking for the etymology or first use of any specific term. As I misunderstand it, there was an organized effort in the 19C to systematize chemical nomenclature, and I'd like to learn about that campaign. Nimur's last reply is in the right neighborhood. —Tamfang (talk) 00:45, 13 August 2020 (UTC)
 * Since I already did the work, I may as well share a few other things I also found:
 * this little blurb, a 2009 IUPAC newsletter about the commemorative stamp, Nomenclature Chimique 1892-1992 from Switzerland
 * This Library of Congress Rare Books Collection entry for Méthode de nomenclature chimique (1787), with a full PDF available at no cost. (It is written in the French language, of course, because what serious 18th-century scientist would write in English, a language of tobacco-farmers and uneducated sailors?)
 * And, excerpts from an unpublished lecture series, Documenting the History of Chemical Nomenclature and Symbolism - with lots of citations to even more full-length books that I haven't read yet. The lectures name-drop a few of the more famous guys - Jöns Jacob Berzelius and Antoine Lavoisier - individuals who I would specifically say used non-modern notation - I mean, when I recreationally read what those guys wrote, they use words and symbols that are pretty different from what I'd find in a 21st-century American high-school chemistry book.  But everything is a matter of interpretation, and this whole bit may be a metaphorical exemplar of Gradualism (in its literal sense, not in its debunked-19th-century-Science sense).
 * So I'd reemphasize the whole "gradual process" and "committee" aspects: no single individual was the person who made standardization occur, and there wasn't a single day that it all happened. Over time, more scientists became more methodological.  As transportation and communication became more commonplace, the scientific community became more well-connected; methods and terminology became more uniform.  A few individual scientists stand out in my mind (as I recall the way that I learned the history of modern science, a pedagogy that I today recognize as a somewhat disingenuous academic sleight-of-hand).  But when you dive deeper, it's easy to find work by every major chemist and physicist and "natural philosopher" of the 19th century who at least makes a passing mention of notation and terminology and taxonomy.
 * Nimur (talk) 14:59, 14 August 2020 (UTC)

Why is Direct Current distinct from Alternating Current?
I understand that both with Direct current (as electrical current from a battery to a receiving device) and with Alternating current (electrical current from a current manufacturing device to a receiving device in a closed electrical orbit or "circuit") there is always a need to create more electrical current to have the receiving device working because electrical current is used until it gets over and new current is needed.

Why does Direct current disntincted from Alternating current? I mean, is this distinction more than a mere physical observation in the sense that it gives some practical benefit?

Big thanks; 182.232.41.11 (talk) 07:01, 7 August 2020 (UTC)


 * Big advantages of direct current:
 * Most electronics uses DC. AC has to be converted to DC to power a computer or cell phone.
 * You can get DC out of a battery.


 * Big advantages of alternating current:
 * You can easily convert it to a higher or lower voltage with a transformer.
 * By using transformers, you can send it over long distances.


 * That last one is why your house has AC. If it was DC they would have to make a bunch of small power plants so that one is close to your house. --Guy Macon (talk) 18:04, 7 August 2020 (UTC)


 * Formerly, DC had one more big advantage: for large motors like the ones in electric trains, AC motors used to be less efficient. I think it was around 1975 that this changed; anyway, this is the reason why many rail systems built before that era, such as older subways, were built to use DC; and since changing everything at once to use AC would be complicated and expensive, generally they still do. --174.89.49.204 (talk) 23:23, 7 August 2020 (UTC)


 * Not just older subway system; railway systems all over Europe began electrification before 1950 and used either DC or low frequency AC, which allows the same simple yet efficient motors as the DC system, but also allows high voltage for transmission. The downside is that it needs a heavier on-board transformer. Some railway systems decided to switch later, leading to mixed systems. But new metro/subway systems tend to use DC too. This is because DC has another advantage not yet mentioned: it doesn't suffer from the skin effect. If limited clearance doesn't allow high voltage (tens of kilovolts), you're stuck with low voltage (hundreds of volts) and high currents (kiloamps) that need big conductors. In big conductors, the skin affect causes AC to have higher resistance than DC. PiusImpavidus (talk) 09:30, 8 August 2020 (UTC)


 * Thanks, I did not know about that as a difference. (As to "not just", I did say "such as".)  --174.89.49.204 (talk) 23:32, 8 August 2020 (UTC)


 * Is this why elevated subways have so many little buildings where the electricity comes in? If it's DC that is. 600 to 660 Volts DC for New York City, don't remember exact number. There's small windowless buildings with lots of conduits between tracks and street canyon wall. Usually not at stations. Underground ones must exist too but would be hard to distinguish from doors to emergency exits etc. Sagittarian Milky Way (talk) 22:27, 7 August 2020 (UTC)


 * I don't know about the specific buildings you refer to, but probably the answer is yes. A subway or similar line using 600 volts DC requires electrical substations at regular intervals to supply the power.  The normal pattern would be to supply AC at a higher voltage to the substations, and each one would rectify it to DC (using a method that depends on the age of the substation) as well as transforming the voltage down. --174.89.49.204 (talk) 23:20, 7 August 2020 (UTC)


 * Those windowless buildings could be either feeder stations, providing DC electricity to the power rail, or cabinets containing the relays that control signals and points (switches). The former should have big cables connecting them to the power rail and the running rails (used for return current), the latter, which should be more common, may have cables connecting them to the running rails (for track circuit train detection). I've never personally observed the elevated railway systems of American cities. PiusImpavidus (talk) 09:30, 8 August 2020 (UTC)
 * Track circuit train detection lol. Something called communication based train control is rolling out but until the 21st century train detection was done by the original 1904 system of handles on hinges on the "ground" that would push a stick under the bogey that dumps the train's brake air if it's driver could've rammed the next train if he was trying to and the ramming train was at max physically possible speed and the next train was still and only inches after a handle and he had previously sabotaged the handle being passed by cutting off the part that pushes the stick. Since this is extremely unlikely the train would instead stop before it rams the next train. The handles also electromechanically know how many handles the next train needs to be in front of you before they turn the hinge so it doesn't move the stick and simultaneously turn one red traffic light yellow and how many to turn the other light yellow and so on till both lights of a traffic light are green. There's also buttons above the driver window when he's at appropriate stations that he can press to move the track bending thingies that switch which track he'll go down next and rooms at major station ends with track diagrams on the wall and indicator light bulbs that show what colors the traffic lights are that fit into this somehow. There are many sheds and I suspect at least some of them may be electromechanical traffic light controllers. There is a metal pan next to the handle too that presumably protects its gizmos. Sagittarian Milky Way (talk) 03:26, 11 August 2020 (UTC)


 * Hence the War of the currents. ←Baseball Bugs What's up, Doc? carrots→ 21:19, 7 August 2020 (UTC)

My complement for your great answer, dear Guy Macon. 182.232.41.11 (talk) 00:34, 8 August 2020 (UTC)

On a slightly different topic, that lack of skin effect, as well as other advantages, actually means if you get up to really high voltages, DC can be more efficient than AC over long distances, which is why HVDC has been growing in popularity as solid-state power electronics have advanced. But again, that's for long-distance transmission links. --47.146.63.87 (talk) 23:46, 8 August 2020 (UTC)

Load paths and structural systems
I’m trying to understand how load paths work. If a single beam can take a point load, does that mean any other beams connected to it through shear connections can also take the point load? Or can something else in the system fail (for example one of the shear connections or another beam in the system) if they have a lower load capacity than the one with the point load. 90.194.50.247 (talk) 10:48, 7 August 2020 (UTC)
 * I myself know very little about Structural mechanics, but from spending several years in an office literally sitting next to structural engineers whose main jobs were designing lattice towers, and checking the structural integrity of existing towers after proposed and actual modifications and load additions by others, I can tell you this: it's a difficult topic and you are unlikely to get information useful to you by asking questions from a forum such as this. You need to listen to and read, and understand, qualified instruction and formal texts on the subject. This matters, because failures in structures due to poor/uninformed design (or build) can and do kill people. {The poster formerly known as 87.81.230.195} 2.217.210.84 (talk) 08:22, 9 August 2020 (UTC)

Old movies Hd
How are old movies released in HD? Is there much of a difference between SD and Hd with old movies? 90.194.50.247 (talk) 19:00, 7 August 2020 (UTC)
 * They typically use an upscaler and sometimes clean up visual artifacts. Killiondude (talk) 19:18, 7 August 2020 (UTC)
 * What's the pixel analog of analog film film anyway? VHS is probably lower-quality upscaling source. Sagittarian Milky Way (talk) 21:55, 7 August 2020 (UTC)
 * I don't think they would be producing HD disks from standard VHS tapes. ←Baseball Bugs What's up, Doc? carrots→ 22:05, 7 August 2020 (UTC)
 * 35mm film apparently has a "resolution" comparable to 4K or 6K (under ideal circumstances; also, the copying process to create release prints was not lossless). Cheers ⌘  hugarheimur 09:27, 8 August 2020 (UTC)
 * Oftentimes, old movies were recorded on film, and that film actually has a high enough resolution (not in a digital sense, but in terms of detail, yes) that, if rescanned from the original film, it can be digitized to HD quality. TV shows, on the other hand, were often recorded on tape rather than film. Tape didn't have that same level of "resolution," and so you need an upscaler for old TV shows, and any movies recorded on tape instead of film. --OuroborosCobra (talk) 02:40, 8 August 2020 (UTC)
 * To be a bit more specific, all old movies were recorded on film, because that was all there was. Usually it was 35 mm film, which as noted above is about as good as HD.  TV shows in the early days were not recorded at all, or were recorded on tape, but 35 mm film eventually became standard after one influential show began doing it: See I Love Lucy#Production. --174.89.49.204 (talk) 05:52, 10 August 2020 (UTC)
 * Kinescope was a method of capturing live TV shows on film, which was not exactly Hi-Def but it was better than nothing. ←Baseball Bugs What's up, Doc? carrots→ 16:46, 10 August 2020 (UTC)

Do fire pits have a way to 'breathe'?
I saw many times videos of people cooking (or baking?) pork in a fire pit by putting the pork inside and sealing this pit tightly (usually by mud) and keep it inside for long time. Do these pits have a way to 'breathe'? any fire needs oxygen, isn't it? Otherwise I really don't understand scientifically how those fire pits works.--ThePupil (talk) 23:06, 7 August 2020 (UTC)
 * Fire pit might have some answers. ←Baseball Bugs What's up, Doc? carrots→ 23:33, 7 August 2020 (UTC)
 * Just by the way, you mean breathe, not breath.  --Trovatore (talk) 23:46, 7 August 2020 (UTC)
 * Thank you. I edited it. I appreciate your note. Who knows how many times I did this mistake and how many times I'd do it unless you noted it. Thank you.--ThePupil (talk) 00:05, 8 August 2020 (UTC)

My guess is that you saw a video of Kālua pork being made. The thing is that it's not really a fire pit. It's not open flame that's cooking the pork; the fire is meant to heat up the stones and vegetation and earth that's doing the cooking...more of an oven than an open-flame kind of deal. You'll want to read earth oven for more details.  bibliomaniac 1  5  00:06, 8 August 2020 (UTC)