Wikipedia:Reference desk/Archives/Science/2018 December 26

= December 26 =

Submarine performance
What was the highest speed ever attained by an American submarine? And how deep was the deepest dive by an American combat submarine (excluding research submarines such as the Alvin or the NR-1)? 2601:646:8A00:A0B3:0:0:0:A5A2 (talk) 01:25, 26 December 2018 (UTC)
 * Anyone who really knows isn't telling. But, it's probably the two ships of the Seawolf class for speed (most power in the least hull), so not the (stretched) USS Jimmy Carter or the Virginias. I know of no reason to believe the Virginia pumpjet is fundamentally different or significantly more efficient.  How fast?  25-35 knots is the range between 'admitted' and 'highest plausible claim'. A more interesting figure is perhaps the fastest speed without becoming unduly noisy, somewhere inbetween.
 * The depth is probably the Virginias, being newer. They all (all three classes mentioned) use HY-100 steel for a high yield strength, thus deeper depth. Given the problems in first welding it with the Seawolves, it's likely that the Virginias may have an advantage from greater experience with it. The admitted depth is "greater than 800 feet" and the likely depth is more like 1600. The test depth achieved so far is highly secret and the operating depth is an arbitrary figure on a piece of paper, but less than this, and also highly secret. It's easier though to estimate the ultimate crush strength at around 2200 feet. Andy Dingley (talk) 03:10, 26 December 2018 (UTC)
 * So, since the most recent records are classified, let me rephrase: What were the highest speed and deepest depth known to have been achieved by an American combat submarine? (And no condition of "without becoming unduly noisy" -- I was thinking about emergency situations, in particular torpedo evasion.) 2601:646:8A00:A0B3:0:0:0:A5A2 (talk) 07:10, 26 December 2018 (UTC)


 * Max Depth is likely around 600m, just like the latest russian Yasen-class submarines which are also the nuclear-powered multipurpose attack type. --Kharon (talk) 12:17, 26 December 2018 (UTC)
 * Ah, yes. The Russian submarine to replace the unaffordably expensive Akula – which ended up costing more than the US subs, and with only one completed. Will the Kazan enter functional service? Who knows!  The Borei are much more likely. Andy Dingley (talk) 13:23, 26 December 2018 (UTC)


 * Why isn't the noise levels of subs from decades ago to like 2010 models classified? That's on Wikipedia. Why isn't the horsepower classified? Sagittarian Milky Way (talk) 03:34, 27 December 2018 (UTC)


 * It has become a profession for multiple international Organisations to collect such data everywhere. The press seems much more interested in that field today than 10-20 years ago i remember. Such data is likely still officially secret and the data is often estimated but its easy to estimate on nuclear submarines since they probably get the same highly reliable optimized reactor module build inside the newest ships as 40 years ago. Anyway the public interest has certainly changed very much. --Kharon (talk) 14:40, 29 December 2018 (UTC)
 * The Borei use the OK-650B reactor from the 1970s. The Yasen has a new design, the KPM 4th generation monobloc from the 1990s. Note that the OK-650 reactor was quite widely used in later Soviet submarines, such as the Oscars. However they had two of them, were smaller than the Borei, and yet the Borei are still claimed to be faster. There are some remarkable improvements in efficiency claimed for the Borei if their claimed performance is to be believed (or not). Andy Dingley (talk) 11:54, 31 December 2018 (UTC)

What happens if you give plants UV-light all night long?
Leave plants by window, sunset, turn UV light on, and sunrise, it turns off. Is this bad for a plant? We already know too much water is bad for a plant, and plants have no selectivity to refuse water. By the way, when photosynthesis equation of sunlight, I'm assuming sunlight is UV radiation, if there's more to it, then what else? Thanks. 67.175.224.138 (talk) 02:51, 26 December 2018 (UTC).
 * In general UV is bad for plants. However it may cause some desirable chemical transformations that improve flavour. Se for example https://www.maximumyield.com/tanning-your-plants-the-curious-effects-of-uva-and-uvb/2/2990 or https://www.ncbi.nlm.nih.gov/pubmed/11567887 or https://growlightinfo.com/the-effect-of-uv-light-on-plants/ Graeme Bartlett (talk) 03:55, 26 December 2018 (UTC)


 * There is such a thing as a Grow light, which attempts to simulate the blend of light you would get from the sun. Pure UV doesn't sound good. You want them to grow, not to get a sunburn. ←Baseball Bugs What's up, Doc? carrots→ 04:50, 26 December 2018 (UTC)


 * There are some crappy traders that try to sell Anti-UV-Foil for Windows who keep spreading the Legend of harmful UV-Light, just to make their product, which is useless, interesting. Unless you live like 5000 above sealevel you should not worrie about UV light exposure, simply because its naturally to little to do seriouse harm. If some plants get harmed, they may generally prefere no direct sunlight and thus dont belong on a windows bench that gets allot of sun during the day. --Kharon (talk) 13:02, 26 December 2018 (UTC)


 * ????? are you referring only to plants or to people indoors? Because if not, "Unless you live like 5000 above sealevel you should not worrie about UV light exposure" is bullshit for many people especially those with fairly light skin tones, as Skin cancers rates attest. (For example, the vast majority of people in NZ or Australia, by far, live well below 5000 above sea level whether you mean metres or feet. Of course if you mean metres, the vast majority of people in the world, by far, live below that.) Nil Einne (talk) 16:12, 26 December 2018 (UTC)
 * There is at least one correct statement in Kharon's comment, that plants that don't like direct sunlight will not do well if placed in a sunny area. ←Baseball Bugs What's up, Doc? carrots→ 16:21, 26 December 2018 (UTC)
 * I took Kharon's comment to mean that you shouldn't worry about UV exposure through a window, which I think is not too unreasonable a claim, at least if you're worried only about acute damage and not about more indirect effects like aging or immunosuppression. To a first approximation, apparently window glass passes "soft" UVA but blocks "harder" UVB and UVC, the sort that causes sunburn.
 * (I should say that even UVA is apparently now considered implicated in skin cancer &mdash; see ultraviolet for more details and refs.)
 * this page claims that window glass will pass almost all light longer than 330 nm, and almost none shorter than that, which I find a bit hard to believe &mdash; if someone has better info I'd be interested to see it. --Trovatore (talk) 22:48, 2 January 2019 (UTC)
 * Excessively intense irradiation can obviously harm plants, and some (e.g. plants that prefer shady conditions) are more sensitive than others; Saintpaulia, for instance, can develop spots and lines on their leaves if cold water touches them in conditions of natural high light intensity.(ref = Pests, Diseases and Disorders of Garden Plants (2000) by Buczacki, S. and Harris, K., p602, HarperCollins). But it seems to me that the OP's question concerns length of light exposure, rather than intensity. The article on photoinhibition states that photosynthesis is inhibited by light, particularly UV light, but it also states that plants have evolved methods to deal with it. Would continuous light be harmful, even if not of very high intensity? An aspect to consider is the effect of continuous light on some plants' systems for initiating certain stages of their growth cycle - see photoperiodism. PaleCloudedWhite (talk) 17:10, 26 December 2018 (UTC)


 * "With every 1000 metres increase in altitude, UV levels increase by 10% to 12%" . Of course excessive sunlight exposure also means excessive UV impact and of course you can get sunburned easily at sea level. I thought that is to trivial to add as info. Go buy all the Anti-UV-Foil you want Nil Einne. --Kharon (talk) 00:34, 27 December 2018 (UTC)
 * Would your average Reynolds Wrap do the trick? ←Baseball Bugs What's up, Doc? carrots→ 00:55, 27 December 2018 (UTC)
 * I never said anything about anti UV foil being worthwhile. Actually I initially said it clearly wasn't but decided it's such a dumb thing to discuss I didn't bother including it in my comment in the end. The fact that anti UV foil is a scam is completely separate from whether or not UV is a serious concern for people living below 5000 feet or metres. The answer of course is it is, as evidenced by the large number of deaths every year which are caused in part by UV exposure from the sun in a number of cases in people who have never visited above 5000 feet, and in many cases in people who spent most of their lives living below 5000 feet and in nearly all cases in people who have never visited above 5000 metres except on an aeroplane (let alone lived). If you had just said that anti UV foil is a scam, I would not have commented, but you didn't instead making the flawed comment that "Unless you live like 5000 above sealevel you should not worrie about UV light exposure, simply because its naturally to little to do seriouse harm". I'm still not sure whether this flaw is because of a serious misunderstanding on your part since as I said, UV light exposure is a serious concern especially to people with fair skin tones even if you're living at sea level if you spend enough time outdoors at the times when UV light levels are high. Or simply a poorly worded comment because of your English ability as you only intended to suggest that UV light exposure to plants or to humans indoors from the sun is not a serious concern. But either way, it doesn't change that your comment was seriously flawed P.S. I also never challenged the fact that UV light levels increase with altitude if everything else is the same. Nil Einne (talk) 01:09, 27 December 2018 (UTC)


 * Okay I'm sorry, I meant photosynthesis-light, not grow-light. Ah yes grow light, I forgot about plants liking red, blue, and white light. But my question is if you gave plant photosynthesis-light 24/7, can they do photosynthesis 24/7? Or do they need a mammalian-equivalent of sleep? Or should I 1st ask, is grow-light and photosynthesis-light the same thing? Same spectrum? Thanks. 67.175.224.138 (talk) 23:05, 27 December 2018 (UTC).


 * Yes, plants have and need their own day-night cycle. Only very primitive "plants" like single cell Algae can be used for endless production cycles aka made to grow 24/7. Some plants can be tricked to some degree by stretching or shortening the daily light exposure and thus extend their growing phase or provoke them to start their bloom and alike, so it seems most plants know from the length of daylight at what time of the year they are, but that is clearly something still counted as rather new researchfield in Agricultural technology. You can find more in scientific sources and field projects in the Web. Just google "Artificial Lighting In Agriculture" or anything alike. --Kharon (talk) 16:20, 29 December 2018 (UTC)

OP, if your interest in this and related questions of plant physiology is more than superficial, you may be interested in What a Plant Knows, by Daniel Chamovitz, a summary of which can be found here. And if you were really fascinated, there's a version of the course designed by Dr. Chamovitz on this topic for Tel Aviv University which is also available on Coursera and the next cohort starts...what do you know--today! Alas though, it seems like Coursera no longer offers the majority of its undergrad-equivalent courses for free as once it did. Still, I can recommend the book at a minimum. Snow let's rap 12:22, 2 January 2019 (UTC)

If the handle of a hammer were less rigid
How would that affect the force of the blow and the ergonomics of using the hammer? --Doroletho (talk) 23:44, 26 December 2018 (UTC)
 * Flail (weapon) might be a good model for research. Ian.thomson (talk) 23:45, 26 December 2018 (UTC)
 * Although not the same, chopping with an axe has similar considerations with regard to handle rigidity. See this guy. I mean, one guesses the force may be very slightly less with a more flexible handle, but ergonomically speaking, the damage to the user will be less. Martinevans123 (talk) 00:05, 27 December 2018 (UTC)


 * Less rigid would mean less secure because it would mean unnecessary movement/flexibility which over time will lose the head. Since all weight is in the head, hammering is all about making the head hit its target in a way the least energy is lead back tru the handle. --Kharon (talk) 00:16, 27 December 2018 (UTC)
 * ????Which is of course directly contradicted by two of Andy's examples, a hammer that is designed to have a springy shaft, and the fact that steel all in one hammers are too stiff. But please do carry on displaying your ignorance to the masses. Greglocock (talk) 07:12, 27 December 2018 (UTC)


 * This is a surprisingly complex topic. People who hammer things all day (and that includes baseball players) get to care very deeply about it. Centre of percussion is the first topic to look at. It doesn't matter much if a hammer shaft is rigid or flexible, inertia means that impact loads don't care that much (the impact load matters a lot, without time for the bending of an elastic shaft to have much influence), but geometry has a great influence.
 * Some hammers have flexible shafts, made of ropes. As it's impractical to have two people swinging a two-handled hammer, heavy hammers (such as used for pounding in fence posts) may use leather straps to lift them, instead of any rigid shaft. You can have four people working one of these, and it works with just a heavy rock too.
 * Swinging a heavy sledgehammer two-handed should be done by moving the grip of one hand up and down the shaft, to either lift the hammer (hands apart), or to bring both together at the sweet spot on the handle, to avoid tiring shocks on your hands. Blacksmithing is also done with very great care to use the length of the shaft fully, but again not going past the sweet spot. A smith may make a lighter blow by swapping to a lighter hammer, or may temporarily hold their regular hammer short-shafted. Bricklaying, where hammering is usually relatively minor, uses a crude 'lump' hammer with a short shaft, and these are unusable for long periods  (if you're chasing grooves all day, swap hammers).
 * The material chosen for a hammer shaft (hickory or ash, sometimes fibreglass today) is there so that the shaft doesn't break. Not because its elasticity or internal damping is particularly easy to use. Although steel-shafted hammers (no-one can explain these) are too rigid, and are horrible to use.
 * Rattan cane handles are used for wooden mallets and some light hammers. This is because they have particularly light heads, and so the shaft needs to be correspondingly lighter, or else the centre of balance is too far down the shaft.
 * One of the few hammers with a deliberately elastic shaft is a silversmith's planishing hammer. This is small, light, with an extra-thin shaft and usually a swollen bulb at the base of the handle, as the main shaft is too narrow to hold easily. It's used with a 'bouncing' motion and a great many very light strokes. Andy Dingley (talk) 00:19, 27 December 2018 (UTC)


 * No clue what Background you, Greglocock or Andy Dingley have but i had an education as professional Mechanic, extended working practice and then an additional education in Mechanical engineering (in Germany). There are all kinds of Hammers so its naturally you also find some special purpose ones that are different, as Andy already pointed out. that does not make my general Answer contradicting. Its just general. --Kharon (talk) 19:18, 27 December 2018 (UTC)
 * Professional mechanical engineer. Greglocock (talk) 19:58, 27 December 2018 (UTC)
 * Professional YouTube viewer. Martinevans123 (talk) 23:09, 27 December 2018 (UTC)
 * Meat popsicle. Andy Dingley (talk) 09:58, 28 December 2018 (UTC)