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March 11[edit]

Jiggling nervously your leg[edit]

Is there a scientific name for the act of jiggling nervously your leg? Is there an article about it, causes and such?--Hofhof (talk) 00:13, 11 March 2018 (UTC)

Google "jiggling leg nervously" and see if you like anything that turns up. ←Baseball Bugs What's up, Doc? carrots→ 00:39, 11 March 2018 (UTC)
No, I didn't like anything that turned up. --Hofhof (talk) 01:51, 11 March 2018 (UTC)
The only thing that comes to mind is Restless legs syndrome, but I think that's somewhat different from what you're describing. Although one good term for it might be "fidgety". ←Baseball Bugs What's up, Doc? carrots→ 02:15, 11 March 2018 (UTC)
Also, see this:[1]Baseball Bugs What's up, Doc? carrots→ 00:42, 11 March 2018 (UTC)
If it's voluntary, you're just jiggling your leg. If it's not, there's restless legs syndrome and focal seizure. But probably you're just jiggling your leg. _ Nunh-huh 02:13, 11 March 2018 (UTC)

You may also be interested in searching for "non-exercise activity thermogenesis", or NEAT. We don't seem to have a specific article on it, but thermogenesis mentions it. --Trovatore (talk) 05:07, 11 March 2018 (UTC)
If I've interpreted Hofhof correctly, then the question is about a semi-voluntary movement at about the frequency of a shiver or a slow tremor that occurs when the leg is in a certain slightly stretched position with the toes on the floor. It can be voluntarily reproduced by many people, but can occur involuntarily when the person is nervous, stressed or cold. I've no idea what it is called, and I can't find an article. It is slightly too fast for a deliberate muscle movement initiated in the brain, so it must be some kind of muscle feedback loop. Dbfirs 12:59, 11 March 2018 (UTC)
At about 5:20 Menashe's right leg begins to move in the way that I think is being described by Hofhof. The movement seen there is faster and with a range of motion shorter than what I have most often observed. But I think this is a very common, rapidly repetitive motion observed in many people. In my experience it always involves a seated person. It may be seen more commonly in males. These are all just my own observances. I have no sources to provide and I know of no references to this sort of thing. But it does seem like it could have a name—be it scientific or otherwise—and it would seem to me likely that it would be described in some literary entity. Bus stop (talk) 13:32, 11 March 2018 (UTC)
Here is a video relating to this phenomenon. And this. And this. I cite these merely as references. Of course I am not endorsing any of the commentary accompanying the references. Bus stop (talk) 13:38, 11 March 2018 (UTC)
See 貧乏揺すり translation just realized I'm doing it myself --catslash (talk) 16:16, 11 March 2018 (UTC)
Googling binboyusuri gets this instructive video. --catslash (talk) 16:27, 11 March 2018 (UTC)
We can say that we have confirmation that others have observed this phenomenon. I am hopeful that Hofhof will weigh in to tell us if what we observe is on the right track. Bus stop (talk) 18:51, 11 March 2018 (UTC)
This language forum thread on the subject also fails to find a name for it. I know a couple of people who have this habit, very annoying when you're sitting on the same settee. This anxiety forum thread finds numerous self-confessed leg-bouncing addicts, but still no name. Alansplodge (talk) 22:03, 11 March 2018 (UTC)
I took this to the Web and found this thread; scrolling down past the psycho-babble I found something that matched my subjective impression, the stretch shortening cycle as a means of establishing the frequency of shaking. However, the way our article puts it, it doesn't sound like much of a cycle, and I couldn't quickly substantiate the claim. The forum also claims that this is a way of using skeletal muscle to improve venous return from the leg, e.g. to prevent deep vein thrombosis; I find this plausible, and confirmed by another forum thread (sigh)... but that one mentions that "sedentary behavior" applies to the general field. Looking that up, I can graduate to a Japan Today article [2] that calls various kinds of foot fidgeting "bimbo-yusuri". This is still a broader term including things like crossing and uncrossing legs, but maybe I've nicked the whale, let's see... apparently in Japan, as with almost anything, people are intimidated against it for fear of discrimination [3], but more importantly, that source cites an actual study about it. Well, "cites" is the wrong word since they do their level best to obfuscate the link, but they couldn't resist the temptation to use the number 12,778, which gets me the Tribune [4] and the name of the journal. Searching their archives for September 2015 got me nowhere, but using the journal name and the magic number I found the article from February 2016, five months after the popular press report - [5] Alarmingly, there seems to be some issue with Sci-Hub over Tor at the moment - should find out more about the latest round of persecutions - but there may be a technical term buried in there somewhere, as well as allegedly a claim that it reduces mortality 30%. Wnt (talk) 15:10, 12 March 2018 (UTC)
Seems like a form of stimming, commonly thought of as something people on the autistic spectrum do, but no reason neurotypicsl people mightn’t also do repetitive muscular activity when they are nervous or bored. It could serve as a way to annoy others until some authority angrily orders you to stop. It seems to make the leg feel better. Maybe it stimulates circulation or just exercises the muscles a bit. Edison (talk) 17:37, 12 March 2018 (UTC)
The word you guys are looking for is fidgeting. Abductive (reasoning) 06:38, 18 March 2018 (UTC)

Ceramic tiles for a sound-proof box?[edit]

A friend in a wamer climate sent me a cryptocurrency ASIC which will give me free heat (he'll pay for the electricity) in my cold climate but I need to build a suitable enclosure to minimise the noise. I have started to use 25 mm MDF and 30 mm sound-deadening foam and this helps a lot but it's still quite noisy. Would it help much to put ceramic tiles between the foam and the MDF? I read that ceramic tiles are sound-reflective due to their hardness and smoothness but I'd like to know whether it's a good idea before I buy any. -- (talk) 07:11, 11 March 2018 (UTC)

In soundproof boxes for printers there would not be any ceramic tile. I suspect it has similar properties to the MDF. Instead the acoustic foam has a textured surface, to reflect the sound in different directions. To improve the performance you can put the box in yet another box, with the inner box resting on a bed of sand. Hopefully there are no windows, and the holes for the air to circulate must also be small enough to impede sound. Another way to change the sound may be to change the fan that I assume is there to a more silent one, or to replace it with fluid cooling. (like water cooling). Graeme Bartlett (talk) 08:03, 11 March 2018 (UTC)
Designing soundproof enclosures rather depends on the frequency content of the sound. You also need to make sure that there is no structural transmission of vibration. Any modern phone will have a spectrum analyser app. Rather trickier is deciding which part of the noise spectrum is annoying you. In general bricks are good, wood is bad. Greglocock (talk) 08:38, 11 March 2018 (UTC)
  • As Greg notes, soundproof enclosure design is complex and depends heavily on the frequencies involved. What are those frequencies, and how are they travelling? Broadly, high frequencies will travel through the air and around corners, low frequencies will go through the walls of the enclosure, or even along those walls.
Your best approach is to reduce the noise generated. I've not seen any of these low-end ASIC machines which have been at all well designed for efficient cooling or low noise. They're not even designed for proper rack mounting. If you look at how servers are racked up, especially blade servers, that might give you some ideas. In general, try to get efficient airflow through the hot parts of the enclosure (maybe not so much over the cooler parts) and keep peak temperatures even everywhere (a cheap IR camera such as the FLIR One [6] is good for this, or even a really simple IR thermometer). It is much more efficient (in air moved / noise dB) to use a single large fan, rather than multiple small fans. Better designed fans will have features like sawtooth fanblade edges and better guard bars. My home office servers are two 20 year old HP Kayak machines, single fan each, because these are still the best designed tower case machines I've seen for airflow - they're now on about their fourth set of motherboards. Even better is to avoid fans as much as possible, by using thermosyphon cooling, although this might work for cooling the rack but you still need fan-forced air to get airflow through the smaller passages around the hotter parts of the board.
For soundproofing, I'd expect this to be medium-higher frequency white noise, rather than low frequencies. If you have mechanical noise, use better fans. If there is mechanical vibration from the fan block, isolate that as a separate unit on rubber blocks or elastic bungees (silicone wristbands are good, and don't age like rubber does in electronics enclosures). Then line the inside of the main case with a foam or wool liner, which absorbs high frequencies rather than reflecting them. A thin layer of rockwool roof insulation under stapled-down netting is cheap. The inlet and outlet ports also need to be lengthened tubes, lined on the inside, so that there's no direct line-of-sight path in an out of the enclosure (or sound will just travel that way). Make sure the ports are big enough to allow good airflow, and their outer edges should be rounded with trumpet bells, not sharp corners. I _wouldn't_ fan blow the entire airflow - allow a lot of it to be thermosyphon, and just use the fans to blow cold inlet air where it's most needed.
Then check the thermal management again, with the sound box in place. Do it again after an hour - recirculated air paths inside can get hotter and hotter.
Mostly I'd look at re-racking these things. As noted, I've not seen one of these coin miner rigs that was competently designed, compared to modern blade servers. Andy Dingley (talk) 11:12, 11 March 2018 (UTC)
Just a follow-up question: something that isolates noise, will also isolate heat. If you are in the same room with the ASIC, the heat will trickle anyway, but how will you avoid the ASIC from over heating? Hofhof (talk) 15:45, 11 March 2018 (UTC)
Its no problem to wrap up a noisy box with enough layers of foam patches to make it silent. Heat transfer/cooling can be silenced too. You either add some liquid cooling system and use its radiator as your heating or you keep using your air/fan cooling but build Labyrinth seal like artificially lengthened paths with similar foam patches separate for your air in- and out channels. The only drawback of the labyrinth approach is the need for some additional space, which is why its usually not used in professional solution no matter its cheaper and more reliable. --Kharon (talk) 17:59, 11 March 2018 (UTC)
In a real life scenario you could also place the ASICs in the basement, and transfer it like in this datacenter in Finland. Hofhof (talk) 18:19, 11 March 2018 (UTC)
Basement? The OP seems to be from the UK. Nil Einne (talk) 04:54, 12 March 2018 (UTC)
  • "something that isolates noise, will also isolate heat"
No. Heat is removed by convection - the physical movement (blown or thermosyphon) of heated air. To do this quietly you need to achieve several things: convection to remove the heat, removing the HF sound from this convecting air (absorbent surfaces on the exhaust duct), not generating any new noise from the air movement (quiet fan designs, quiet inlets and outlets without resonances or sharp corners), not transmitting any LF conduction noise through the structure. Andy Dingley (talk) 20:31, 11 March 2018 (UTC)
To be more precise: if something produces heat at a roughly constant rate within a box, on the long run what is within the box does not matter to the heat that is exchanged with the outside (the power output observed outside is the same as inside, because thermodynamics). What might happen though is that a critical part of the something overheats and fails, so if you want to avoid that, you need some kind of thermal exchanger and (as described above) those will put a price tag on the "noiseless" requirement. TigraanClick here to contact me 17:04, 12 March 2018 (UTC)

Poisonous orchid?[edit]

Is there really a species of orchid which is native to the jungles of Brazil and which is poisonous to humans, but not to most animals? Or did Ian Fleming invent it, just as he invented "skin suffocation"? 2601:646:8E01:7E0B:71B8:6856:E929:5E71 (talk) 09:58, 11 March 2018 (UTC)

A quick googlesearch on "poisonous orchids" brings up several assertions that "there are no known poisonous orchids", but I wouldn't be inclined to trust absolutely anything not coming from professional botanists. However, the frequency of such claims in the present day suggests that Fleming wouldn't have known of any claimed or actual poisonous orchid when he wrote the book, and therefore likely invented it. The books were intended as light entertainment, so I doubt Fleming would have bothered to carry out deep research for such a minor detail: that it seems plausible to his readers would have been sufficient for his purposes. {The poster formerly known as} (talk) 12:19, 11 March 2018 (UTC)
Some interesting material here. If Fleming had a bunch of ornithology books kicking around, maybe he had that book as well? Matt Deres (talk) 01:59, 13 March 2018 (UTC)
Can you elaborate? I can't read the source -- it's paywalled! 2601:646:8E01:7E0B:0:0:0:64DA (talk) 06:35, 13 March 2018 (UTC)

Invasion of a home by ants[edit]

Yes, I do have this situation. We've lived here for about 3 years and only about 3 months ago, in the middle of the winter the pests began coming in. With the weather getting warmer their numbers multiplied. There is only one small area in one of the bathrooms affected, perhaps 3 feet wide. My wife, naturally, goes nuts. I called the exterminators and made an appointment. Immediately my daughter and son-in-law came for a visit and said: cancel it, they will kill your cat and poison you.

Is it a realistic scenario?

Thanks, AboutFace 22 (talk) 16:41, 11 March 2018 (UTC)

We have had periodic spraying for ants and other pests, and our cats and ourselves are just fine. Once the spray they use has dried (about half an hour) then it's safe to put your cat back on the floor. ←Baseball Bugs What's up, Doc? carrots→ 16:50, 11 March 2018 (UTC)
ants in your house? Realistic. They will kill your cat? Possible. They will poison you? Unrealistic. I use AntRid. Greglocock (talk) 17:09, 11 March 2018 (UTC)
A professonal exterminator might also have a theory on why they're (apparently) only there, where they're coming in, and what they're feeding on. Ants don't come into your house to be annoying, they come in looking for food. ←Baseball Bugs What's up, Doc? carrots→ 17:13, 11 March 2018 (UTC)
Professionals fight Insects with specific poisons which are no serious thread to Mamals aka breastfeeding species. Nevertheless they are still poisons so pets and children should be kept away. Ants should be easy to fight off without poisons and they usually can not do any harm unless they are Fireants or another of the very few dangerous ant species. Best read a bit about ants and try to identify the sort simply by finding out what ant species are common in your area. Ask your wife to find out about them on the internet so she maybe looses her fear. --Kharon (talk) 17:27, 11 March 2018 (UTC)

Thank you. Every contribution is valuable. AboutFace 22 (talk) 18:31, 11 March 2018 (UTC)

I'll just note that what works against one species of ants may not work against another. I live in Toronto and there are two kinds of ants that get into my house from time to time: one species that I've seen for decades and another species about half the size that I've only been seeing for maybe 10 years. For the first species, I can buy what the stores call ant traps or ant baits. Since Wikipedia doesn't have an article under either name, I'll explain: these are little containers that you punch a hole in and set down on the floor or wherever the ants ago. The idea is that the ants go into the container, mistake the toxin for food, and carry it back to where they live. However, in my experience this method doesn't work at all against the smaller ants. For them I use an aerosol insecticide that you spray onto the floor and it leaves a residue. It has been effective against that species and hasn't hurt our cats, but I'm not presenting this as general advice. A professional who sees the ants might know what will work against the ones you have. But on the other hand it might cost a good deal more than the right product you can buy in a store, if you know what the right product is. Maybe you should talk to your neighbors. -- (talk) 18:48, 11 March 2018 (UTC)
We do have Pest_control#Poisoned_bait- it briefly mentions ant and roach baits, but isn't that informative. This is in the section on Physical_pest_control, but our dedicated article on Physical_pest_control doesn't currently include anything on insect baits. Anyone else find relevant WP articles? Seems like a big weakness, at the least some redirects may help in the short term. SemanticMantis (talk) 02:13, 12 March 2018 (UTC)
  • You've essentially omitted all the information needed to get a useful answer. Where do you live? A place where ants can survive outside in winter? Or is the source colony inside your building somewhere? How are they getting into your bathroom? What kind of ants are they? Looie496 (talk) 23:44, 11 March 2018 (UTC)
Agreed, those details are all very important for determining what the ant problem is and how to solve it! But I'm not so sure they help answer the question asked: whether it is realistic that a local exterminator will kill pets and human residents when hired to get rid of ants. I'd WP:OR rank both human and pet death as "extremely unlikely" when dealing with a licensed professional, but I have no WP:CRYSTAL.
I'd encourage OP to specify these and perhaps ask a new question if they want references and info on dealing with ants in the house :) SemanticMantis (talk) 02:05, 12 March 2018 (UTC)
In this country infestations are almost always of ghost ants or pharaoh ants. I thought these were alternative names for the same insect but there is a difference. The preferred method of treatment is to smear bait around the crevices from which they emerge. This clings to their bodies and they take it back to their nest, where it renders the queens infertile. (talk) 12:45, 12 March 2018 (UTC)
Which country? Your answer doesn't match your IP geolocation. Dbfirs 13:17, 12 March 2018 (UTC)

I will try to answer some of the questions, however I doubt the answers will help me to combat the problem. I live in Salt Lake City, Utah, suburbs. We had a rather brief but significant period of snowfalls and the ants began to come in in small numbers first when there was at least 2 feet of snow in the yard, right under the place where the bathroom counter with two sinks is located. They crawl from under that counter and travel across a tile floor. I was wondering how could they survive out there, very mysterious. Now it is of course much warmer, the snow is gone. I did buy a trap at and will try to set it up today, perhaps in less than an hour. I will try to read other posts and see if I missed some questions I need to answer. I will also try to measure the ants. Thank you all. AboutFace 22 (talk) 16:58, 12 March 2018 (UTC)

Many ants such as ghost ants and carpenter ants depend heavily on a water source. Either a leak from the sink or condensation forming on pipes could help sustain them, as could leaks from snow piled on rooftops that forms ice dams and leaves water to seep inward etc. If you stop the water, you should stop the ants for good. Wnt (talk) 18:06, 12 March 2018 (UTC)
Rather than measure the ants, just take a photo of them crawling over a ruler and post that. We can tell more from the image (but that is only to satisfy our intellectual curiosity), ( it may also indicate that they are ants that thrive in a moist eviromet) . As said above. If you live in the civilized world, your pest exterminator will be licensed to indicate that they are competent enough to place 'poisons' in a domestic residence in a way that will not poison your pets (but at a great cost to you and they will have to come back to repeat the treatment again and again, year after year). Modern ant treatments (bought off Amazon) come with instructions that inform the home owner where to place it the so they don't accidentally poison pets. Finally, don’t matter what type of ants you're infested with. Good old inexpensive borax and sugar is efficacious against all ants. Maybe it is because it is old fashioned and not dependant on the latest high tech chemistry (promoted heavily by the chemical companies that have developed them), it has been ignored by modern home owners with more money than sense. However, don't ignore your daughter and son-in-law concern. Some household quick-solutions can be very detrimental both to you, your cat and anybody else living under your roof. --Aspro (talk) 19:04, 12 March 2018 (UTC)

Again thanks for contributing. I am embarrassed to say that I cannot add much information now. I went home on my lunch break and did not have enough time to install the traps but my wife said something that attracted my attention. She said that there were no ants today. Is it possible that they kept coming in in cold weather just to get warm and now when the temperature is outside they don't need us? It needs further investigation though. AboutFace 22 (talk) 20:29, 12 March 2018 (UTC)

When your wife said “that there were no ants today” it means the same as she didn't 'see' any ants today. Doesn’t mean that there where no ants. But don't fret. Sounds like you don't have a bad infestation. The trap you bought will probably work well. But what about next year? Borax & Sugar is so cheap and is only mildly toxic. Place it where cats can't get at it (but ants can) and you might start missing them. Ants are ecologically fit to recycle organic matter – like the warm damp wood in your bathroom when it is cold outside. But borax will not only deprive them (and their poor little baby ants) from a living but will kill them too. Might make the chemical companies very upset, that your not buying their very expensive products. Yet what do you want to spend your money on? Making them rich or getting rid of your ants? And they are your ants. If you provide a suitable habitat for mother nature to colonize -you only have yourself to blame. --Aspro (talk) 21:37, 12 March 2018 (UTC)
Borax is a chemical compound, and can be harmful to children and pets in sufficient quantity. I remember that it was no magic bullet where some roaches I had were concerned. But a good exterminator, besides deploying toxins one hopes are non-toxic, will also give you recommendations about any leakage of water; so if he's coming, you might as well try to dry up any such sources in advance so as to give him more time to poison the ants. Wnt (talk) 00:26, 13 March 2018 (UTC)

Yep, @Aspro is correct, I should not have said that. It turned out to be a "fake news." Later in the day she was crawling on the floor collecting them with a wet wad of paper. She uses soapy water for that. Realistically I cannot do much in terms of setting traps for them until Friday - when my weekend starts, I am really too busy every day at work and with domestic chores too. However I really appreciate all the contribution and will use them in my fight against the ants. AboutFace 22 (talk) 15:07, 13 March 2018 (UTC)

Ants hate cinnamon, if you want to exclude them from a food source... Abductive (reasoning) 06:41, 18 March 2018 (UTC)
I didn't know about cinnamon, but when the kitchen was infested by ants I solved the problem by placing the food in a dish which I balanced on a tumbler in a bowl. I then filled the bowl with water to form a moat. The ants realised the game was up and disappeared within a few hours. Of course, if you possess a refrigerator you could put the food inside, since it appears they don't like cold either. (talk) 16:35, 18 March 2018 (UTC)

March 12[edit]

carnivore eats carnivore[edit]

Why do most carnivores prefer to eat herbivores and not other carnivores? Are herbivores tastier?2A02:8109:89C0:8AC:C40F:313C:7952:AC96 (talk) 15:42, 12 March 2018 (UTC)

That's an observation for mammals, but not fish. Anyone care to expand on that aspect? Andy Dingley (talk) 16:32, 12 March 2018 (UTC)
Even herbivorous can inflict life threatening injuries to a carnivore during the hunt (with horns and hoves). Should a carnivore animal pick a fight with another carnivore animal, neither is likely to come away uninjured. From a survival point of view, it is not worth the risk. Unless a big carnivore chances upon a small carnivore. In that case, carnivore do eat other carnivores. --Aspro (talk) 16:39, 12 March 2018 (UTC)
So it's only humans who do "Dog Eat Dog"?[7]Baseball Bugs What's up, Doc? carrots→ 18:26, 12 March 2018 (UTC)
Dogs do, too. 2601:646:8E01:7E0B:0:0:0:64DA (talk) 06:37, 13 March 2018 (UTC)
(e/c)Herbivores are easier to catch and don't pose the same threat as another carnivore. I suspect they are tastier; perhaps someone who has eaten dog meat could confirm. Bushmeat is known to spread disease. Hyenas and vultures are not so fussy but they always let someone or something else do the killing.--Shantavira|feed me 16:41, 12 March 2018 (UTC)
(edit conflict) Even among mammals, lions will predate the cubs of other big cats or of wild dogs if they have the opportunity. An apparent preference for berbivores may simply be because herbivores are (a) more common than carnivores and (b) don't have sharp teeth and claws. Gandalf61 (talk) 16:44, 12 March 2018 (UTC)
Trophic level. In particular the ten percent law says that 100 pounds of herbivore flesh only sustain 10 pounds of Level 2 carnivore and 1 pound of Level 3 carnivore. So, carnivore eating carnivores are rare, though certainly they make an impression. Note that cold-blooded animals are more efficient, hence more interesting chains among fish in the ocean. Wnt (talk) 17:59, 12 March 2018 (UTC)
This answer is so correct we could probably close the thread. To summarize a simply as possible (at the risk of imprecise phrasing): food energy derives from the sun, via plants. Plants use a portion of this energy to grow. Herbivores eat the plants and then use a portion of that energy to grow and/or live as well. Carnivores and carrion eaters eat herbivores and then use a portion of that energy to grow/live as well. Even if carnivores and carrion eaters were as easy to eat as herbivores (they almost are for modern human hunters), it's no where near as rewarding. Carnivores would have to be ten times easier to hunt just to be equally worthwhile. Cougars would have to be in the habit of breaking in to our houses and exploding into already butchered and cooked to be more useful than cows. Ian.thomson (talk) 18:19, 12 March 2018 (UTC)
Err, no, a cougar is likely about as nutritious as a herbivore of the same mass. The problem is that in order to "keep" a cougar, you need to provide it with ten times its weight in herbivores, and in that case you get 10x more food if you just eat the herbivores yourself. (talk) 21:26, 12 March 2018 (UTC)
What’s the err bit for? The above doesn’t suggest that carnivore meat (like cougar) is more nutritious . Carnivorous are just further up the food chain. --Aspro (talk) 21:50, 12 March 2018 (UTC)
"Carnivores would have to be ten times easier to hunt just to be equally worthwhile." - this is the part that I disagreed with, that to me implies that carnivore meat is 10x less nutritious. That's not the issue (and probably not the reality, although we humans mostly dislike land carnivore meat for some reason) - the issue is that if you're a level 3 carnivore, you have to wait for your prey to feed and grow, and you use up a much higher share of the ecosystem in doing so than if you were level 2. That means that the ecosystem can support 10x smaller population of your species (going with the 10x estimate). If your species can also eat herbivores, it will be able to support a larger population than that, but that doesn't say anything about the nutriotiousness of carnivore meals. (talk) 00:06, 13 March 2018 (UTC)
There is no rule or system other than big eats small aka Opportunism for carnivores. For example Sperm whales only eat squids, who are also carnivores and even often cannibalistic. Most seals eat fish, sea lions even specialize on penguins and sea birds and are themselves hunted by Sharks and Killer whale. Only the offspring is typically spared by its own parents and species. --Kharon (talk) 21:28, 12 March 2018 (UTC)
I think is on-target here, and Ian and Wnt, generally reliable contributors, have missed the boat on this one. As 93 alludes to, the ultimate energy cost of the meat is a consideration for a rancher, but is unlikely to interest a predator.
It does seem plausible, though, that predators might avoid prey higher in the food chain to avoid higher concentrations of toxic substances; see biomagnification. From "plausible" to "true" is a big leap, and I don't know whether there is any good research on it. --Trovatore (talk) 21:40, 12 March 2018 (UTC)
A relevant question may be: what is the earliest carnivorous life on earth? Another relevant question may be: what is the earliest herbivorous life on earth? And a third relevant question concerns the truth or falsity of the hypothesis that most carnivores eat herbivores. If we know that herbivores preceded carnivores in the evolution of life on Earth, and if it is the case that most carnivores eat herbivores, then the reason for the present arrangement can be a consequence of the order in which the two types of life forms came into existence on Earth. Bus stop (talk) 22:38, 12 March 2018 (UTC)
@Trovatore: At no point did I suggest that carnivore meat is more nutritious. My point is 1) you need 100 pounds of herbivore meat to keep 10 pounds of carnivore meat living, if it feeds on herbivores, and 2) you need 10 pounds of carnivore meat to keep 1 pound of carnivore-eating carnivore meat living. Which means that if all sizes are equal, you expect to find 100 herbivores roaming around for every 10 carnivores that kill herbivores and every 1 carnivore that kills carnivores. Now to dispel an idea someone started pursuing above, this does not mean that purely carnivore-killing carnivores can't exist; they do because they have a distinct ecological niche, which means, if there are sufficiently few of them on a frontier, they can eat well because not much else could compete with them to eat those particular carnivores that are their prey, guaranteeing some equilibrium number can exist. Wnt (talk) 00:02, 13 March 2018 (UTC)
I think the question does not concern ecological niche. Sure there can be exceptions. But generally speaking, does most life on Earth follow the principle of carnivore eats herbivore? An ecological niche can be an exception to what generally is the case. Bus stop (talk) 00:10, 13 March 2018 (UTC)
By "ecological niche" I mean that you can always support a certain number of mongooses in their natural habitat, because nobody and nothing else is crazy enough to mess with a cobra. (* this is not really altogether true, but amusing) Wnt (talk) 00:19, 13 March 2018 (UTC)
And cobras are carnivores. But perhaps this arrangement is an exception to a general principle prevailing over the entirety of life forms on Earth. Bus stop (talk) 00:27, 13 March 2018 (UTC)
Well, eating carnivores has a higher ultimate energy cost, but the point is that the predator doesn't pay that cost. It's a pure externality. So you seem to have a missing step in your argument, if you claim that's the reason that predators prey less on animals higher on the food chain.
You might be just saying there are fewer of them around to eat? --Trovatore (talk) 00:29, 13 March 2018 (UTC)
The "balance of power" between herbivores and carnivores is a result of an as yet unidentified factor. I am suggesting a ratio of available nutritional value is a consequence of the order that these two classes of life came into existence. The first carnivores fed on herbivores, assuming that is the order in which they came into existence. I am suggesting that from that earlier point in time to the present, that ratio has been resistant to drastic change. Bus stop (talk) 00:42, 13 March 2018 (UTC)
The above was actually a response to Wnt. --Trovatore (talk) 00:49, 13 March 2018 (UTC)
I know it. I'm just trying to clarify my hypothesis. Bus stop (talk) 00:57, 13 March 2018 (UTC)
Yes, I was just saying there were fewer around to eat, and explaining the reason for that.
As for the "order of the two classes of life", that's basically balderdash. Sure, there's a "Carnivora", but in general there are a lot of omnivores and the ecology is relatively labile. As a generalization, mammals all pretty much look and act like rats (well, shrews if you want to use the favored description of the common ancestor), and will typically go back and forth from devouring grain, grasshoppers, or misfortunate fellow mammals pretty freely. Out of that, on occasion, some have developed more predictable tendencies, sometimes (as with panda bears) not what you'd expect. Wnt (talk) 02:09, 13 March 2018 (UTC)
How does one intelligently respond to the question "Why do most carnivores prefer to eat herbivores and not other carnivores? Are herbivores tastier?" So far, I don't see any answer emerging from the responses. At least, we should be intelligent enough to ask the relevant questions. Are the inbuilt assumptions correct? Do most carnivores eat herbivores? Bus stop (talk) 03:05, 13 March 2018 (UTC)
They have to, because about 90% of the available meat is herbivore, as I explained above. Wnt (talk) 21:59, 13 March 2018 (UTC)
@Wnt: As I understood the question, the claim is that predators selectively prefer herbivore meat. If that is true (I don't know whether it is), then saying there's more herbivore meat around is not really an answer.
It could be part of an answer, if you claim that the predators have to make specializations to eat one or the other, so it makes more sense to eat the one there's more of. But that's a separate claim that needs to be separately asserted and defended. Without it, the claim about prevalence is kind of a non sequitur. --Trovatore (talk) 17:50, 14 March 2018 (UTC)
Perhaps I took for granted that predators would occupy some knowable position in a food chain, yes. A hypothetical predator (Pac-Man) that can catch and devour any flesh the same way should have no preference. But if a predator needs to have any adaptation to catch specific prey, then for every one predator specialist there will be ten herbivore specialists ... provided the chances of catching and eating the food are the same, which admittedly I don't know. Even at the cultural level we tend to specialize -- there are some people who like to go out and hunt bear year after year, but most people choose deer because there are more of them. And people who regularly hunt deer wouldn't quite know how to hunt or cook a bear, so given one bullet and a choice, you might expect them to look for more deer. Wnt (talk) 19:02, 14 March 2018 (UTC)
Apart from the 90% of meat locked up in herbivores as Wnt points out, there is also the animal physiology to deal with. predators have evolved to kill, they have sharp teeth and claws, while herbivores have evolved to only prevent themselves from being eaten, but that hasn't led to a body design that's very lethal to predators. Herbivores have not evolved to be stronger or to be able to outrun predators either. Many herbivores have instead evolved to live in large herds and they are then protected by being safe in numbers. Basically the herd gives predators that hunt them what they want so that the vast majority of the herd members will survive. Evolution of the herbivores due to the pressure of predation is then driven more by competition within the herd than by competition between the herbivores and predators. A herd member is safe as long has it is not the slowest of the group, there is no need to be faster or stronger than the predator. Count Iblis (talk) 22:52, 13 March 2018 (UTC)
I suspect, but cannot prove, there is more to it than this. I have the impression that any herbivorous species like the dodo in the absence of predators will tend to degenerate, so that contrasted with another species subject to predators it has no chance to survive, and so in that sense the predator and prey are essentially symbiotic -- at the species level, that is. In the case of the dodo, of course, predators can be blamed for their demise, but I do wonder if an object lesson can be found where an herbivore literally became extinct through the lack of predation and ordinary levels of environmental change. Wnt (talk) 23:15, 13 March 2018 (UTC)
So the answer to the question originally posed is: availability, or as Trovatore said, "You might be just saying there are fewer of them around to eat?" Bus stop (talk) 23:11, 13 March 2018 (UTC)
See where I said "Yes", above. Wnt (talk) 23:16, 13 March 2018 (UTC)
OK, I stand corrected. Bus stop (talk) 00:36, 14 March 2018 (UTC)
'Degenerate' is a weird word to use in evolutionary contexts. NZ had very few mammals and no real land mammalian predators [8] (also earlier article). There were a small number of bird predators like the Haast's eagle and Ruru (Morepork) but on the whole, it's probably fair to say there were far few predators of larger animals than in many other locations. Species in NZ therefore evolved in this relatively predator free environment and many birds for example spend a lot of time on the ground with a number being completely flightless. With the introduction of mammalian predators particularly rats, ferrets, stoats, cats, dogs and for some humans (I mean as direct predators); many of animals have problems coping. Habitat and other largely human induced changes don't help either. This shouldn't be that surprising with a basic understanding of evolution. But how would these species compete in a pristine NZ (including fauna) with other herbivore birds etc. Some like rabbits would I suspect do well, probably even in a pristine NZ. But will all do so? BTW, in terms of the general question, I think this is one (of many) cases where we have to be careful about just so stories or simplistic answers. There's a reasonable chance a number of different factors in combination (albeit often related) have given rise to the rarity of carnivorous predation of other carnivores. I'd note also that many or even probably most predatory animals seem willing to be scavengers when the opportunity arises, as far as I know there's no evidence of much bias against scavenging other carnivores. I think even the bias again their own species tends to be a lot less than most people expect. Nil Einne (talk) 10:09, 15 March 2018 (UTC)

Y-chromosome inference[edit]

To what extent and with how much confidence can a man's Y chromosome be reconstructed, if only his daughters' and their mothers' genomes and biographies are available? (talk) 21:58, 12 March 2018 (UTC)

According to Y chromosome, "95% of the human Y chromosome is unable to recombine", meaning that at most 5% of genetic material from the man's Y-chromosome can find its way into his daughters' genome. Even if this happens (and the change of it happening increases with the number of daughters), it is impossible to say whether any such material originating from the father comes from his Y-chromosome or from his X-chromosome. So in conclusion, I'd say that you can at most reconstruct 5% of the Y-chromosome, and your confidence is low, unless perhaps the probability of recombination is well known and there are lots of daughters for statistics. - Lindert (talk) 22:27, 12 March 2018 (UTC)
Well, if you can do a complete gene sequence of the pseudoautosomal region of both the mother and a daughter, then you should be able to identify regions of sequence that are, in their entirety, from the man, and can be used to identify the man from a sufficiently large and detailed database of the sort that you pretty much know that spies have probably amassed by now in secret. Crossovers in the pseudoautosomal region are actually obligatory [9] and hence such sequence should nearly always be available. That paper describes 220 single nucleotide polymorphisms in the region; the data seems to be available here. Wnt (talk) 00:18, 13 March 2018 (UTC)
Oh, whoops ... that answer conflicted with the premise that only those genomes were available. Without other data, it is possible to identify which chromosome came from the mother, and hence which is from the father, but as Lindert says only the 5% would be known and it wouldn't be known which chromosome that was from. Perhaps some extra deductions could be made using data beyond the simple sequence, such as gene imprinting data (expression of transcripts), DNA methylation, even histone modifications, which might indicate portions of the chromosome that are definitely from the father's Y. Wnt (talk) 23:24, 13 March 2018 (UTC)

U Value for glass[edit]

Hi All, just wondering if anyone can tell me, U Value = watts/m2 Degrees Celsius is the calculation to work the U value out but it gives no time frame, is this worked out per hour or day or what ? — Preceding unsigned comment added by (talk) 23:31, 12 March 2018 (UTC)

The Watts unit already includes the characteristic dimension of time, meaning Joules per second. Our writings are available at U value. Graeme Bartlett (talk) 00:03, 13 March 2018 (UTC)
Oops ... yes, that's what the OP was actually asking. ;)
I did a web search and the top hit was [10], which I think is a commercial site but gives .22, .25, and .30 as typical values for window units (not just the glass, which as a theoretical continuous surface would be more efficient). They say .30 is a cutoff for federal tax credits, presumably in the U.S. Wnt (talk) 00:07, 13 March 2018 (UTC)
Example, say U-value is 1.1 Wm−2K−1. Your sheet of glass is 2 square meters and you want to keep the temperature 20°C warmer on the inside compared to outside. This would then say energy conduced through is 2×20×1.1 = 44 Watts. In an hour this would be 44×3600 158,400 Joules, or in a day 44×3600×24 = 3,801,600 Joules, close to 1 kilowatt hour. Graeme Bartlett (talk) 00:15, 13 March 2018 (UTC)

March 13[edit]

What is the reason that it's not recommended to put hot foods in the refrigerator?[edit]

Normally people don't put hot food in the refrigerator. Is there a basis for that? if there is, what is the reason for that? (talk) 00:34, 13 March 2018 (UTC)

If the food's too hot and too big (i.e. it has too much thermal energy), it can warm up the contents of the refrigerator so rapidly that the cooling equipment can't keep up, so you'll end up warming the refrigerator's interior too much. Nyttend (talk) 00:40, 13 March 2018 (UTC)
Hot food will produce allot of water vapor that will condense and freeze at the cooling element, building up a growing ice coat around it which prevents the fridge to cool down the air effective. Its also a waste of energy because the hot food will cool down fast without investing additional electrical energy with the fridge. Additionally the whole concept of preservation with a refrigerator is to keep the temperature low enough to keep all microorganisms in a Hibernation state. Every time the food gets warm again the microorganisms start eating and reproducing, thereby cutting down the time of the food they are on to the state of spoiled. So its no imminent drama if you put some hot food into your fridge but its still wrong in many ways. --Kharon (talk) 05:23, 13 March 2018 (UTC)
Also the water vapor from the hot food will condense ON the hot food as well and make it soggy. 2601:646:8E01:7E0B:0:0:0:64DA (talk) 06:41, 13 March 2018 (UTC)
Also, if the hot food is in a type of container that will crack from thermal shock, you don't want that to happen. -- (talk) 16:54, 13 March 2018 (UTC)
I used to keep pot of boiled milk in refrigerator. Did so every day for a week or two. The acrylic sheet on which I used to keep the pot gradually developed cracks due to sudden temperature difference. Now I let it cool down a bit but when it is still hot I put in refrigerator to cool it quickly to prevent growth of microbes. manya (talk) 07:45, 13 March 2018 (UTC)
The best way to cool an item like this is to immerse it in cold water for a while, rather than put it in the refrigerator, for the reasons listed above. --TammyMoet (talk) 13:05, 13 March 2018 (UTC)
The problem that the contents of the fridge will heat up if you put hot stuff into it, is a lot worse with modern fridges that are a lot more energy efficient compared to older ones. Old fridges with poor thermal insulation can more easily deal with hot food, because they are pumping out heat at a much faster rate anyway. To store freshly prepared food you should cool it asap using e.g. cold water as suggested above. I usually put the food cooled in this way in the freezing compartment of the fridge, not to freeze it but to cool it rapidly down to just above freezing point. Also, the freezing compartment is isolated from the rest of the fridge, and the fridge will start to work immediately if you put something in there, while if you put something in the fridge, it will only start to cool the contents if the temperature rises above a set point. The faster you cool the food to below 10 C the better, a rule of thumb is that every hour at room temperature takes away about one day of safe storage time at fridge temperatures. Count Iblis (talk) 18:35, 13 March 2018 (UTC)
I just stick it outside for a few minutes. At −37 °C (−35 °F) it don't take long. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 23:03, 13 March 2018 (UTC)
Err. What do you do in those few short and very long summer days in Cambridge Bay when temperature it gets up into in to the 80's ? Do you just eat Eat MacDonald's hamburgers and French fry takeaways? Come on. You must have fridge, otherwise you beer will go off. Oh! That is providing you're allowed to drink beer up there  :¬) --Aspro (talk) 16:27, 15 March 2018 (UTC)
I'm not sure the last time I saw 80 °F (27 °C). Couple of summers ago we were in Hay River, Northwest Territories and it was 25 °C (77 °F) and that was more than hot enough. For MacDonald's I would need to go to Yellowknife and the return fare is over $2,000 so not really worth it. Of course we can get take-out burgers and fries from any of the 5 restaurants in town. Beer is allowed here but again you have to get it from Yellowknife, so hard liquor gives you the best value. And every house has a fridge and most houses will have a chest freezer as well. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 12:44, 16 March 2018 (UTC)

Cormorant identification[edit]

Cormorants at the Jamestown Ferry

What species are these? They looked more like Phalacrocorax auritus than any other North American species I found, but these look green, not the black of this species. But maybe it's my colorblindness, making me imagine that I'm seeing a dark green when it's really black. Nyttend (talk) 00:35, 13 March 2018 (UTC)

I'm not good with cormorants, but these don't appear green to me. However, while I have perfect colour vision, I'm not sure we can trust this image's colours as it has clearly been altered to compensate for the low-light. Matt Deres (talk) 02:03, 13 March 2018 (UTC)
Well, I used flash, but it's just as it came from the camera; I don't have any photo-editing software aside from Windows Paint. Nyttend (talk) 02:27, 13 March 2018 (UTC)
Yes, but the camera itself has built-in imaging software that takes the picture from raw data to jpeg. - Nunh-huh 05:29, 13 March 2018 (UTC)
Ah, okay; I thought this meant that it had been photoshopped. Nyttend (talk) 12:11, 13 March 2018 (UTC)

That definitely looks like a Double-crested cormorant to me. Though in the image given in that linked article, there are clearly some green shades. Polyamorph (talk) 12:17, 13 March 2018 (UTC)

Sterilizing hamsters[edit]

Miniature hamsters I bought (here in China) used to breed. Now they do not. I buy new ones when they die of old age. I suspect the wholesaler gives them some drug just before selling them to stop them from breeding. Is this possible. Anna Frodesiak (talk) 13:07, 13 March 2018 (UTC)

The answer may be more simple. “Warning. The following may read like something that has just come out of the Twilight Zone.“ You know how the Monsanto company spend billions convincing us that the GM's are safe and they are, - aren’t they? Because Monsanto spend billions cherry picking scientific proof that shows no health issues. But what about the Glyphosate herbicides? I just had to google Hamsters, Glyphosate, and Infertility and loads of stuff comes up. American human fertility rates are plummeting ( there could be other reasons for this but this includes couples that are desperately trying to start a family). What are you feeding your hamster on? The cheap GM stuff from the pet store? Make your own mind up. Please report back on how you got them breeding again. --Aspro (talk) 14:56, 13 March 2018 (UTC)
@Aspro: I just had to google Hamsters, Glyphosate, and Infertility and loads of stuff comes up. If you googled "moon landing hoax" or "electrosensibility health scandal" or "homeopathy discredited by Big Pharma" or "Holocaust did not happen" or "how dowsing works" or anything of the kind you would also have seen loads of stuff come up. You inconsciously preselected what conclusion you expected, the query reflected that and the results obliged.
Now I know next to nothing about hamsters, fertility, and glyphosphate, and it may well be that you are correct. But you should really, really, really have put up sources rather than giving a rant with vague pointers (and prefacing it with a warning that is is a rant does not make it any less a rant).
For instance, here's a serious-looking source that says (see paragraph I.C) that GM crops in China are mostly limited to cotton and papaya (at least until 2010), i.e. not stuff hamsters eat. Presumably the OP's hamsters are fed on local (=Chinese) pet food. TigraanClick here to contact me 16:53, 13 March 2018 (UTC)
  • As this is the science desk, I need to point out that Aspro's rant above has no basis in peer-reviewed science. Read it at your own peril. Fgf10 (talk) 18:44, 13 March 2018 (UTC)
Perhaps they stopped selling you females? Greglocock (talk) 15:45, 13 March 2018 (UTC)
I have not heard of terminator technology being used on livestock, but I cannot formally rule it out. I know of less-than-reversible sorts of male contraception like cottonseed oil that affect humans ... no idea how it affects a miniature hamster. I also have no idea if the entire randy colony of hamsters has simply caught a bad case of chlamydia (apparently Chlamydia muridarum does infect hamsters, according to our article), nor whether that sterilizes hamsters. In biology anything is possible, but not much is likely. Wnt (talk) 23:31, 13 March 2018 (UTC)

Just to let you all know, we feed the hamsters grains we buy, like whole oats, and also vegetables and peanuts. No pet store food.

Also, this sterility is present in the last few groups of around 8 hamsters we bought. We just got a new group and they are still too young to breed. We shall see. Anna Frodesiak (talk) 01:07, 14 March 2018 (UTC)

Ooh, I just found Chemical castration. Could the wholesaler get a hold of some of these chemicals, like SpayVac? Anna Frodesiak (talk) 01:09, 14 March 2018 (UTC)

Chemical castration isn't really permanent, and it seems like an added expense is implausible. I mean, it seems more conceivable (or at least more amusing) to picture a hamster assembly line passing beneath automated robot assembly probes that implant intrauterine devices in all the females. (I suppose every once in a while they get a male by accident, or the maintenance technician's finger, with tragic results) Wnt (talk) 03:11, 14 March 2018 (UTC)
But suppose a wholesaler could give the hamsters something in their food just before sale that would stop them from having babies. Their sales would increase. Anna Frodesiak (talk) 12:10, 14 March 2018 (UTC)
I was going to say I never heard of any such thing and doubted it was possible, but naturally I just had to try a quick web search first... came across [11]. Here is the PubChem entry. Says it causes ovarian tumors in mice but not in rats, and "in mice, the ED50 for the reduction in small oocytes by 4-vinylcyclohexene was 2.7 mmol/kg, whereas, no detectable oocyte loss occurred in rats at the highest dose of 4-vinylcyclohexene (7.4 mmol/kg)." PubChem as a compilation isn't exceptionally reliable, but it copied that abstract from here. Another study says " 4-vinylcyclohexene diepoxide (VCD, 40 mg/kg), was used to induce premature ovarian failure (POF). Methylparaben (MP, 100 mg/kg), propylparaben (PP, 100 mg/kg), and butylparaben (BP, 100 mg/kg) dissolved in corn oil were treated in female 8-week-old Sprague-Dawley rat for 5 weeks." [12] It also has some effect on hamsters: "Siberian hamsters were treated with VCD (240mg/kg i.p. daily for 10 days) during short days, and outcomes were compared with reproductively active females that were maintained and treated in long days. Primordial follicle numbers were significantly reduced by VCD under both day lengths, and reproductive quiescence in short days did not appear to render the ovaries less susceptible to VCD-induced follicle depletion." [13] I don't know if it works on proles but given the widespread use as an industrial chemical I imagine the data should be available. Wnt (talk) 15:30, 14 March 2018 (UTC)
Holy moly, Wnt. I think that may be it. Anna Frodesiak (talk) 19:24, 18 March 2018 (UTC)

Thank you all for the very thoughtful answers! Anna Frodesiak (talk) 19:24, 18 March 2018 (UTC)

Discarded plastic bags everywhere while there is a shortage of fuel[edit]

I watched a documentary, and it showed people using discarded plastic bags as cooking fuel. The people were breathing fumes. Is there a cooker that can burn old plastic bags without harming people? Anna Frodesiak (talk) 13:10, 13 March 2018 (UTC)

Bags are, in general, polyethylene. As a fuel it's pretty clean. As a pure hydrocarbon it contains only carbon and hydrogen, so the exhaust products will be carbon dioxide and water vapour. At worst, if burned in restricted airflow, carbon monoxide.
PVC, also used to make thin films for packaging, is another matter. The chlorine content is a problem if you're going to burn it, as are the plasticizers. Andy Dingley (talk) 16:24, 13 March 2018 (UTC)
The fact that the completely burned products are safe does not make burning the substance itself safe. One of the byproducts of incomplete combustion of polyethylene is surely going to be ethylene oxide. For that, the CDC states, "Ethylene oxide gas may produce immediate local irritation of the skin, eyes, and upper respiratory tract. At high concentrations, it may cause an immediate or delayed accumulation of fluid in the lungs. Inhalation of ethylene oxide can produce CNS depression, and in extreme cases, respiratory distress and coma. In some persons, ethylene oxide exposure may result in allergic sensitization, and future exposure may cause hives or a life-threatening allergic reaction." Looie496 (talk) 16:56, 13 March 2018 (UTC)
Whilst ethylene oxide wouldn't be a good thing, you're not going to produce that (or at least, not release a significant quantity of it) for a typical polyethylene flame in an adequate air supply. Andy Dingley (talk) 17:34, 13 March 2018 (UTC)
Google for diesel from waste plastic and take also a look on The Ocean Cleanup project. There are some people from India and also in Saxony, Germany. Buying meat in a super market today, You get a plastic package made from several plastics and coatings of several other plastics to keep fresh and save material. Conventional plastic recycling on this fails caused by the several different plastic types in one piece of plastic. Later production should be a process like performed in an oil refinery. --Hans Haase (有问题吗) 18:13, 13 March 2018 (UTC)
Plasticizer chemicals have a potential to be very harmful since they are suspected to interfere with human hormones. However "fuel" can contain very harmful chemicals as well, especially in developing countries where unrefined Crude oil is often used, since these can contain for example Naturally occurring radioactive materials and other poisons. --Kharon (talk) 12:14, 14 March 2018 (UTC)
"adequate air supply" may be the sticking point here. Many cooking fires are extremely inefficient.
Stoves, even simple camping stoves, with proper air-flow can greatly improve the quality of life for people still relying on cooking stoves. At least, that's the premise of a number of businesses and charities that supply such stoves to third-world countries. BioLite#HomeStove is the first one that comes to mind, but there are a few of them. ApLundell (talk) 00:09, 16 March 2018 (UTC)
Hi ApLundell. So, can that run on old plastic bags? Anna Frodesiak (talk) 07:15, 16 March 2018 (UTC)
"Improved cooking stoves" have been a stalwart of the appropriate technology movement since the start. Victor Papanek, for one, has written about them. Andy Dingley (talk) 10:19, 16 March 2018 (UTC)

What I'm getting at is a stove that safely runs on plastic bags. It would stop people from getting sick from fumes, would provide fuel, and kids would be running around gathering old bags for mom, which would clean up the environment too. Is there such a stove?

Anna Frodesiak (talk) 07:15, 16 March 2018 (UTC)

No, there is not. Almost every kind of plastic will release toxic fumes when burned, to a greater or lesser extent. They will burn, but they will not be safe to burn. BastunĖġáḍβáś₮ŭŃ! 09:23, 16 March 2018 (UTC)
There are a couple companies apparently talking about offering stoves intended to burn plastic. The one that seems farthest along is the Energant K2, which claims to be able to safely burn fuel that is up to 8% plastic. [14] Modern high-efficiency stoves can reduce smoke by ~95%, and the same high efficiency helps to more thoroughly burn the fuel and reduce the number of toxic products. This would obviously be an advantage if one is going to try burning plastic. Of course, it also matters what you burn. Burning polyethylene is already much less hazardous than burning PVC or fluorinated plastics. However, it seems like their product development has stalled since they discussed it more than 3 years ago but it is still not available for purchase as far as I can tell. Perhaps the idea of a safe stove burning (small amounts) of plastic was still more wishful thinking than reality. Dragons flight (talk) 11:11, 16 March 2018 (UTC)
I guess, You will find the information, You are looking for in Polyoxymethylene dimethyl ethers (OME), (in German Polyoxymethylendimethylether or Oxymethylendimethylether). --Hans Haase (有问题吗) 08:19, 17 March 2018 (UTC)
Bastun, never safe, understood. Dragons flight, only 8% max., and wishful thinking on the best stove yet, understood. Pity. Hans Haase, thank you dear, but I found nothing much there. Anna Frodesiak (talk) 19:36, 18 March 2018 (UTC)

Oh, well. Thank you all for taking the time. I guess Earth and its silly fools will all have to live with these trillions of plastic bags everywhere. (Oh, and I just saw someone buy a bundle of zippy bags in a larger zippy bag and the shopkeeper put them in a bag for the customer. I'm not kidding. I asked why, and he said because that bag had a handle. Sorry Earth. We're not that bright.) Anna Frodesiak (talk) 19:36, 18 March 2018 (UTC)

Vitamin K[edit]

I switched to a multivitamin that does not have vitamin K like my old one, since I still want vitamin K I plan to get it from food. The vitamin k article lists vitamin k1 (mainly in certain vegetables) and k2 (mainly in meat and dairy), but my old vitamin just says vitamin k. Does it matter which one you take? I am also confused by how much you need, since my vitamin lists the amount you need in mcg but wiki lists it as IU, what is the conversion?--User777123 (talk) 18:58, 13 March 2018 (UTC)

In case you don't know, mcg is a terrible way of writing μg, the actual unit. That might help with your searches. Fgf10 (talk) 19:35, 13 March 2018 (UTC)
Actually, it is not a bad way, but you're right it won't do well in searches and is widely considered obsolete. I just tried out Google and got four different sets of results with µg (using the HTML version), μg, microgram, and mcg. But it could be worse ... in the old days people would use pre-Unicode word processors where µ is just an "m" in symbol font, and inevitably they would mess with their fonts at the last minute before submitting a draft, which means that any "mg" published in the 1990s is like as not to be micrograms. I suspect, but do not know, that the Venezuelan horses killed by selenium were victims of something similar involving their home pharmacy's special recipe. Wnt (talk) 21:57, 13 March 2018 (UTC)
Your body actually stores, and uses, vitamin K2 (unless you are really a vegetable). However, any K1 in your diet gets converted to K2 by the bacteria in your gut - so it makes no significant difference which one you take. Wymspen (talk) 23:28, 13 March 2018 (UTC)
I've seen claims vitamin K is not even something that needs to be supplemented in most people with ordinary diets, an attitude our article reports but not enthusiastically. There are many people on warfarin whom doctors believe need to have less vitamin K activity than their diet would naturally provide. On one hand, there is thrombosis, heart attacks and strokes, death; on the other side uncontrolled bleeding, shock, ischemia, hematomas, death. You pay your money and take your chances. Wnt (talk) 23:38, 13 March 2018 (UTC)
  • Trying to answer the OP's question, I don't see where Wikipedia lists Vitamin K recomendations in IU. There may not be an IU measurement for Vitamin K (each vitamin has it's own IU standard that is developed individually, it's... confusing) and Vitamin K and Reference Daily Intake and Dietary Reference Intake list recommended Vitamin K intakes in micrograms. I'm not sure where on Wikipedia the OP is seeing it listed in IUs. But if they are looking for Vitamin K recomendations, there's three sources that list it in micrograms. --Jayron32 19:27, 14 March 2018 (UTC)

March 14[edit]

Elbow skin[edit]

Does the skin on human elbows have a special scientific name, and if so what is it? FreeKnowledgeCreator (talk) 02:28, 14 March 2018 (UTC)

There is no term for the skin. It is not wenis or wagina, as Google searching will tell you. (talk) 09:57, 14 March 2018 (UTC)
If you refer to thickened skin areas these are generally called Callus or in this case simply "elbow callus". --Kharon (talk) 11:59, 14 March 2018 (UTC)
You can certainly develop a callus on your elbow - it's possible - but the loose flap of skin there has more to do with the natural loss of elastin and collagen in skin as it ages. As a major joint, the skin gets stretched at the elbow and, with age, it ceases to rebound as it used to. Regardless, I'm pretty sure this question has to do with the "wenis" or "weenis" hoax going around. Matt Deres (talk) 02:57, 15 March 2018 (UTC)
Uh, no, not really. I don't follow puerile hoaxes. It was just a question, and Kharon answered it in a satisfactory manner. FreeKnowledgeCreator (talk) 02:03, 17 March 2018 (UTC)
If you follow that line, you get a specific answer to the question, as was done by this IP editor:

See here:[15].

- 15:45, 15 March 2018

can any odor be smelled during rain?[edit]

If there is a decomposing carcass, can the stink be smelled during a heavy downpour? Thanks. — Preceding unsigned comment added by (talk) 14:29, 14 March 2018 (UTC)

Yes of course. Even humans notice the "clean" smell in and after a thunderstorm, which is actually a rise of ozon particles in the air. As you may know many animals have superior Olfaction, some a million times more sensible than human senses. They can even smell unterwater! --Kharon (talk) 17:07, 14 March 2018 (UTC)
You probably mean ozone, not "ozon". The smell of ozone is more irritating than pleasant. As Matt Deres says below, the topic is more fully treated in our article about petrichor, a word that will be familiar to Dr Who fans. --Trovatore (talk) 22:09, 14 March 2018 (UTC)
And in case someone invokes the old trope about the smell of "ozone" at the seaside, that smell is actually rotting seaweed. {The poster formerly known as} (talk) 21:37, 15 March 2018 (UTC)
Ozone Park must've been named by someone misinformed. Sagittarian Milky Way (talk) 20:52, 16 March 2018 (UTC)
Recent research indicates that it depends on the specific odor. A 2017 paper in Science titled Poor human olfaction is a 19th-century myth says "When an appropriate range of odors is tested, humans outperform laboratory rodents and dogs in detecting some odors while being less sensitive to other odors. Like other mammals, humans can distinguish among an incredible number of odors and can even follow outdoor scent trails." [16] [17] CodeTalker (talk) 19:14, 14 March 2018 (UTC)
See also petrichor for the general "smell of rain". Matt Deres (talk) 21:08, 14 March 2018 (UTC)

Why do my sunglasses make purple look white?[edit]

I got them at a Dollar Store that only charges a dollar for everything, so they're nothing special. Here is more about them. A sign at a college near where I live changes every few seconds, and if the words or background look white without the sunglasses, they look purple with them.— Vchimpanzee • talk • contributions • 16:24, 14 March 2018 (UTC)

You know, the for $1.5 pairs from the gas station make purple look like...purple. You get what you pay for I guess ;) —SerialNumber54129...speculates 17:18, 14 March 2018 (UTC)
I would hypothesize that the sign that changes every few minutes uses something like a light emitting diode that emits in a fairly narrow range of frequencies to produce each of three colors (RGB). Purple is R + B, which are transmitted well by the sunglasses, but the narrow peak of green light might be at the same frequency as a dye in the sunglasses. Perhaps the maker of the sunglasses, sort of like the maker of the display but in reverse, assumes that if you block out R and G and B in roughly equal amounts, the effect is simply a darkening of what the user sees. But if there is a narrow-frequency source that happens to match a narrow-frequency absorption, then the output will be very different to the human eye than expected! Wnt (talk) 18:52, 14 March 2018 (UTC)
Wnt has nailed it. "Looks white" is no longer any guarantee that some light source is "white", just that it fools eyes into thinking it is. This was an issue for a long time with fluorescent tubes, but with ubiquitous LEDs it's now becoming very obvious. I'm fitting a paint booth into my workshop and I've just gone back to incandescent lights for it, as the other lighting makes it impossible to correctly [sic] judge paint colours. Andy Dingley (talk) 19:05, 14 March 2018 (UTC)
You could do it with graphene. [18] You could do anything with graphene if you could do anything with graphene... actually though, I thought there was a trick for converting laser light to "white" light using non-graphene foam, or something, which I'm afraid I've forgotten, and I wonder if there's some other comparable technology. Wnt (talk) 19:16, 14 March 2018 (UTC)
It's quite likely that we'll see graphene or other metamaterials replacing existing phosphors in future lighting technologies. Their ability to act as broad-band phosphors gives much more natural lighting, rather than the few narrow spectral lines of RGB LEDs in combination, which are increasingly making any general lighting into an Ishihara plate. Andy Dingley (talk) 20:46, 14 March 2018 (UTC)

I wouldn't say the spectra of decent high CRI white LEDs is 'few narrow spectral lines in combination' although it's true they still have peaks. But then again so does much of what people call natural light to some extent. [19] [20] [21] [22] [23]. (I've tried to find decent research articles to include although maybe they aren't always the best. I believe one of the problems is that while there is a lot of research, quite a lot of it is proprietary and not that well published.)

Of course Colour rendering index isn't perfect as we know [24] (also our article). Still by now, most real developers (I.E. not the cheap Chinese factories trying to tick some box) of high CRI LEDs have moved beyond simply having high CRIs, including ensuring high R9 values one of the common weakpoints and often also high Colour Quality Scale too. Probably other things too, if you're actually in the market for high colour reproduction white LEDs, I suggest you look in more detail. For example, I think TLCI is still generally a separate thing from high CRI if that's something that matters to you. But maybe you can find some which achieve both.

Anyway whatever personal opinions of high colour rendering white LEDs, 'a few narrow spectral lines' seems high questionable. I mean even the classic white LEDs which has clear spectral deficiencies isn't really that, it's still fairly continuous. (See the earlier sources or the later ones.) We aren't talking about ancient fluorescent lights here.

Well unless you count light outside the visible spectrum but the obvious question is why? Efficiency demands suggest to me it's unlikely there will be that much usage of LEDs with significant light outside the visible spectrum except for specialised purposes like grow lights (and these will probably often be intentionally different from natural light). I mean I don't know what 'visible light' is for cats and dogs but I can't help thinking that pet friendly LED lights is always going to be a small market. If you have specific reasons for wanting non visible light, then I guess most LEDs suck for your purposes, but that doesn't mean most people have these demands.

BTW in case these is some confusion, the classic white LED is often only a blue LED with a yellow phosphor generally, Cerium-doped Yttrium aluminium garnet, [25] [26]. No RGB is involved. Modern high CRI LEDs generally have a more complex phosphor mix but I don't know if it's accurate to call this mix RGB. Probably RYB if you include the original blue component of the LED since I think one of the common things is to add a red phosphor. Some of the even fancier ones possibly add more, but even then I think many still have the yellow, so maybe you'll have RYGB or something. (I'm sure someone can find a R-G phosphor B LED, but I'd like to see some evidence this is a common thing.) You can get RGB LEDs but these are a rarity used for specific applications (LEDs which let you change colours for purposes including colour changing signs like Wnt mentioned) as they cost more and have other disadvantages.

As for graphene or metamaterials, never say never. But I'm far from convinced it's definite. We are getting good at using what we have, so IMO there will need to either be a significant efficiency or performance improment other than pure spectral one, cost or ease of production advantage (which probably ultimately comes down to cost anyway). See for example these comments from a researcher [27]. Of course it's a promotional story from the university and I don't even know how well recognised the person is in the field, and even if they are reputable they're only one person.

But if we look more widely, while there is interest in different production techniques, including graphene [28] [29] [30], one of biggest areas of active research seems to be quantum dot LEDs for general illumination (and not just displays) [31] [32] [33] so AFAIK not what are generally called metamaterials (although Graphene quantum dot is one are of interest [34]). And you'd note in both cases while colour rendering is mentioned, what they concentrate on is efficiency and other such gains.

Actually this is also reflected in the research articles on high CRI white LEDs. One of the big issues is how to add red without adding too much infrared or losing efficiency or luminous efficacy for other reasons. Getting a consistent colour spectra is also desirable since Product binning adds cost etc especially if you end up with too many of the stuff you don't want. (Well there are also other things like lifespan, including consistent colour and CRI over that life, as well as uniformity of light, how temperature affects performance and life, etc. Different technologies may or may not help with these.)

Particularly with the concern of blue light and circadian rhythms, there is increasing interest in tunable CCT and adjusting blue light level, while maintaining a high CRI [35] [36] (also the earlier one on graphene quantum dot). But even if this does become widespread, however it is achieved, if anything this speaks against an excessively broad spectrum. You don't want one that's only a few lines sure, but you want full one largely only within the visible light range and where you can cut down the blue light when you desire.

Nil Einne (talk) 07:52, 15 March 2018 (UTC)C)

Reading Wnt's source, I guess one issue I didn't touch on is the blue peak. This is something which it's true is still not dealt with by phosphor converted blue LEDs. It's probably true there's no easy solution. Proposals have includes phosphor converted violet LEDs instead of blue [37], but this has concerns including whether violet is actually any better. The other alternative would be to abandon phosphor conversion. I'm not convinced replacing current phosphors with graphene or something else would work, you'd likely need to modify basic operating principles and stop simply converting blue light . For many purposes you could probably simply filter the peak but with an obvious loss of efficiency/luminous efficacy. The obvious question is how much of a concern the blue peak is. Even per my comment above about concerns of blue light and circadian rhythms, as shown in the above sources the blue peak for low CCT high CRI lights tends to be rather small since you don't need much light in the blue part of the spectrum anyway so want to convert most of it. If you want higher CCT lights the blue peak is a bigger issue especially since it means your spectrum tends to be rather limited in part of the blue spectrum, although these aren't very popular in a lot of the West particularly in domestic settings for various reasons anyway. Still use in offices etc means this is an area of active research hence the violet LED proposals etc. Nil Einne (talk) 08:18, 15 March 2018 (UTC)
  • This is a good reason to be careful with very cheap sunglasses. Often they just use coloured plastic or glass to block some wavelengths of visible light. This does nothing about ultraviolet, which is what can damage your eyes, and in fact - because the darker light makes your pupils open wider - they can increase your exposure to dangerous UV. If you can get a UV light source, I'd recommend testing these glasses to make sure they're safe. One easy way to do it is demonstrated here - just shine the UV light through the glasses onto a banknote, and see if the watermark appears. Smurrayinchester 08:37, 15 March 2018 (UTC)
  • "..if the words or background look white without the sunglasses, they look purple with them", this is the exact opposite of what the title is. If the sunglasses make white appear purple I would worry that they are providing no ultraviolet protection at all whilst blocking the middle of the visible spectrum which would be quite bad for you in sunshine as your pupils would be wider with them on. Dmcq (talk) 14:33, 18 March 2018 (UTC)

March 15[edit]

What weapon (or tool) is in this picture?[edit]

In the image in [38], what is this guy holding in his hand? If this is a gun, shouldn't he put it in a safer position? Like muzzle pointing down or up? --Doroletho (talk) 02:59, 15 March 2018 (UTC)

Knitting needles EvergreenFir (talk) 03:04, 15 March 2018 (UTC)
I assume you mean on his lap. Cause if you definitely meant in his hand, what Evergreen said :). It's a short-barreled assault rifle with a foregrip, flashlight, optics, bipod and stock attached. Not sure what model it is, but the strange thing about this gun to me is that there's no obvious place to put a magazine, especially with the bolt looking like it's right above the trigger. So then the obvious place for the magazine would be inside the pistol grip, which would suggest this is a pistol-calibre assault rifle. Looking at such guns online, it resembles an MPA30DMG. Hopefully, he has the safety on and/or the gun is unloaded, though for safety you should do both of those, and have the barrel pointed in a safe direction. Someguy1221 (talk) 06:01, 15 March 2018 (UTC)
My guess is that it's one of the IWI ACE family (also looks like an Israeli soldier to me). Alansplodge (talk) 08:54, 15 March 2018 (UTC)
But those don't have a bullpup configuration. After a quick check I would suggest he has something like the IWI Tavor X95. Rmvandijk (talk) 13:26, 15 March 2018 (UTC)
Agreed. Alansplodge (talk) 22:18, 15 March 2018 (UTC)
There are many potential ways to make this situation appear safer, but I do wonder what the cultural / professional expectation is here. If other members of his unit saw this photo, would they criticize him for not having the barrel pointed in a safer direction (e.g. towards the floor)? Or would they simply assume the weapon is unloaded and not worry about the way it is positioned? Such judgments are often shaped by both written guidelines and cultural expectations. Dragons flight (talk) 10:13, 15 March 2018 (UTC)
Its shurely a X95 in some configuration. Israeli forces are in a civil war for 30-40 years now? We can assume they know what they are doing when handling weapons. You can be harmed by a car as well and statistically it looks as if weapons are saver than cars, given everyone carries or drives them around in countries like Israel or the United States. The only point is, what some people in the United States keep missing, that not everyone is fit to drive a car or carry firearms. That is where the danger is. Not in laying your machinegun in your lap or driving your kids to school in your car, when you have learned how to handle that savely. --Kharon (talk) 14:03, 15 March 2018 (UTC)
Of course many Americans are born into places where it's so inconvenient to do anything without a car that getting a license and passing car inspection is made easy. Perhaps to partially compensate speed limits also tend to be slower than much of Europe (112.65kph might be the most common by population). Sagittarian Milky Way (talk) 02:45, 16 March 2018 (UTC)
There are speed limits everywhere in Europe aswell. Only the famous Autobahn 8D in Germany is an exception. Also everyone easily getting a license, to drive a car or own a firearm, may not be the main problem as long as there are enough checks to make sure the unfit loose theirs fast. --Kharon (talk) 05:41, 16 March 2018 (UTC)
SMW didn't say there were no speed limits. EU rather than Europe but [39] says

speed limit for motorways in EU Member States is mostly 120 or 130 km/h. Germany does not have a general speed limit for motorways, but a recommended speed of 130 km/h. The general speed limit for rural roads in EU Member States is mostly 80 or 90 km/h and for urban roads 50 km/h.

So if it's true motorway speed limits in the US are often only 112.65 km/h, this does seem lower than common in the EU. I'm not sure if their claim is accurate though as Speed limits in the United States by jurisdiction says

Speed limits in the United States vary depending on jurisdiction, with 75 to 80 mph (120 to 130 km/h) common in the Western United States and 65 to 75 mph (100 to 120 km/h) common in the Eastern United States.

Admittedly the map shows the most populous Western state by far is excluded from this 'common' thing so maybe the population bit makes it true. Nil Einne (talk) 07:10, 16 March 2018 (UTC)
There's an inverse correlation of population density with speed limit in the US.
A thing the Wikipedia map doesn't usually show is urban Interstates (translation: E-road/4+ lane Australian National Route)are often slower than rural and not all stretches of rural Interstate have the highest limit of its state (many suburban miles count as urban). If this is common in Europe too that wouldn't be a difference though of course. For a few years after the national speed limit ended 104.6/88.5kph rural/urban motorway was I believe much more common but advances in car tech had encouraged states to raise them (with some holdouts i.e. New York State). From 1974 to 1987 it was 88.5kph nationwide but that was only because the federal oil conservation law was stricter then (yet the raising it to 104.6 on rural motorways was vehemently opposed by the National Safety Council, Public Citizen, Mothers Against Drunk Driving and the Insurance Institute for Highway Safety) Sagittarian Milky Way (talk) 20:28, 16 March 2018 (UTC)
I think this has a lot more to do with lobbies like those you pointed out forming "high-speed" and "low-speed" camps and disabusing politicians of any courage to change the status quo than anything else. Personally, I have not noticed any correlation in national speed limits and general road quality in Europe, although a common factor among most places is that the enforcement is more lax than in the US. (talk) 00:25, 17 March 2018 (UTC)
"On the best estimate, about an eighth of the whole [Autobahn] network of 13,000km (8,000 miles) has no speed limit and about a third has a permanent limit, with the bit between coming and going according to need". [40] Alansplodge (talk) 15:55, 16 March 2018 (UTC)

Threshhold value of stimulus for triggering ejaculation[edit]

How can the intensity of stimulus necessary for triggering ejaculation be expressed in some physical-physiological units and what is its threshhold intensity or numerical value?-- (talk) 23:58, 15 March 2018 (UTC)

For some research on this topic, see here [41], here [42] and here [43]. SemanticMantis (talk) 01:46, 16 March 2018 (UTC)
Some things are better measured by qualitative research than by metrics. Klbrain (talk) 00:15, 18 March 2018 (UTC)
"When you can measure what you are speaking about, and express it in numbers, you know something about it." Lord Kelvin. Dmcq (talk) 09:26, 18 March 2018 (UTC)

March 16[edit]

How can a pedestrian bridge fail so quickly?[edit]

Tragic news from Florida. I know it'd be speculation at this point, but surely this is one of the surest things to design for? Imagine Reason (talk) 01:57, 16 March 2018 (UTC)

I've been warning people to avoid speculation at the article, but there are several possibilities. One of the supports could have shifted or been pushed out of alignment (one appears to be tilted, but that could be an effect rather than a cause). There could have been an undetected flaw in the reinforcing connections, or a post-tensioning cable could have failed. Post-tensioned structures are designed to withstand cable failures within reason, but a failure is a spectacular event that could have unforeseen results - they release a lot of energy. Failures like this usually are the result of a bad connection of some kind. The design appears to be a kind of cable-stayed structure, but the component that failed was apparently designed to support itself during construction without the stays. This newspaper article [44] contains a great deal of speculation, but it describes some of the common adjustments that are made to this kind of structure, such as camber adjustment. Construction is often the most hazardous time for a structure, as the redundant systems of a fully-completed design are not in place and the structure may be subject to unusual stresses. Acroterion (talk) 02:10, 16 March 2018 (UTC)
Your link doesn't work, you lost an l at the end [45]. I also came across this from the same paper which IMO is a little better as while it's speculates on possible reasons, it makes it clearer it is just speculation and doesn't really suggest anything is the cause of he collapse [46]. Nil Einne (talk) 05:31, 16 March 2018 (UTC)
Oops, sorry. Here's another article that's fairly measured in its coverage [47]. Our article on L'Ambiance Plaza collapse is worth a read, as it also involved the placement of prestressed concrete structure that was fabricated elsewhere - in that case the movement was vertical, not horizontal. At L'Ambiance it was apparently a problem with evenly distributed support that led to a failure at a connection point. We can expect reports from construction standards organizations in the long run for the FIU accident. Acroterion (talk) 12:22, 16 March 2018 (UTC)
According to this report, the cables were being tightened after a stress test. Akld guy (talk) 21:40, 16 March 2018 (UTC)
Courtesy link to thus unfamiliar: Florida International University pedestrian bridge collapse. Matt Deres (talk) 12:47, 18 March 2018 (UTC)

sending probe on Sedna[edit]

In 2076, planetoid 90377 Sedna reaches perihelion. Why dont the humans try to land a probe on sedna? I mean, if it lands successfully; it will be a free journey for a very very long distance. All have to be done is to tell the probe to "stay still" and "do nothing" for a few centuries. Once sedna is far long, the probe cab be awaken. Then it can study the outer rim, and edge of solar system. It will take around 12,000 years for sedna to reach the perihelion again. During that time, the probe can go to sleep again. It doesnt need to return by itself. In 12,000 years humans might have gone extinct, or must have built faster space ships. One of such ship can pick-up the probe.

Are there any plans of a mission similar to this? If not, why? —usernamekiran(talk) 12:44, 16 March 2018 (UTC)

It's not that much of a "free journey". It takes considerable energy to match the velocity of such a body. If you can do that, then the probe could have simply put itself into such an orbit anyway. A rendezvous and sampling mission is interesting in itself, see Philae et al, but it doesn't really change the orbital dynamics of a mission. Andy Dingley (talk) 13:02, 16 March 2018 (UTC)
To amplify Andy's point, landing a probe does not provide a "free journey" at all. There is a way to get assistance from an orbiting body such as a planet or asteroid, but it doesn't involve a landing; you have to do a slingshot maneuver. If the probe was able to bounce off a hard object like an idealized rubber ball, then bouncing off the asteroid would give the same benefit that a slingshot maneuver does. (That's because in the asteroid's frame of reference the slingshotting probe is in a hyperbolic orbit.) -- (talk) 20:15, 16 March 2018 (UTC)
My gut feeling is that for a slow trip to put a permanent memorial on Sedna with minimum fuel expenditure, it would be better for it to be moving away from the Sun. That's because our probe, when it eventually reaches the dwarf planet, will need to slow down and otherwise change velocity to match its orbit, and that is easier if it's moving away than if it is moving sideways or coming toward Earth. The idea is delta v. This would not be the case if you wanted as fast a trip as feasible with a lot of fuel to burn, in which case the distance is what matters most. Wnt (talk) 21:48, 16 March 2018 (UTC)
Voyager 1 crossed the Heliosphere of our sun on August 25, 2012. Voyager 2 is currently still in the Heliosheath, aiming to measure its thickness. So the "study the outer rim, and edge of solar system" is already under way and done.
The United States dont seem as dedicated to the Space Race anymore tho its participation in the joint venture James Webb Space Telescope, in preparation to be launched 2019, will probably deliver more new science than all of the historic "spaceprobes" together. Other states dont seem to have very big plans too. Maybe that changes, maybe someone is secretly planning to become/send the first martian (Mr. Musk?). Btw. planning for the second space telescope (James Webb) started in 1996, more than 20 years(!) ago, so its not like finding a target and starting a probe to it some month later. The process to get politics to decide about the money for it can easily take a decade alone. --Kharon (talk) 23:13, 16 March 2018 (UTC)

Aphelion versus perihelion at those distances actually doesn't have much of an effect on the minimum fuel cost of the mission. The vast bulk of the fuel is simply spent getting off of Earth, and then out of its orbit [48]. It would certainly be faster to go when Sedna is closer to the Sun, but still crazy expensive. Also, from an engineer/scientist/politician's perspective, it would be kind of silly to launch something now, intended to go into hibernation for 60 years (and we can't possibly test in advance if it can survive for that long), when instead would could spend money on something that would yield results now, and not even think about visiting Sedna until its much closer. Someguy1221 (talk) 01:43, 17 March 2018 (UTC)

I'm assuming that the OP is thinking about planning/preparing for this now rather than necessarily launching it now although I agree it's way too far advanced. That said, in addition to all the problems highlighted above there seems to be another big challenge. If putting something into hibernation for 60 years is tricky, and I agree it is, imagine trying to put it into hibernation for a few centuries! I'm not convinced our current tech is able to produce electronics that can survive that long, especially in outer space, even given some protection by the planetoid. Even the power source is likely to be tricky. The Radioisotope thermoelectric generator plans using Americium-241 would probably do although with RTGs being in hibernation is irrelevant to the power source (don't know about the other components); hence most plans don't propose that. And as you've indicated there's both producing things that can last that long, and being confident they will last that long. Nil Einne (talk) 04:03, 17 March 2018 (UTC)
In theory Sedna could contribute useful resources, such as water for propellant and ores for solar panels and mirrors. There is no way to rule out some kind of geothermal energy, even toasty warm spots, without a better look-see. But you'd better bring a very big nuclear plant with you if you need power to mine enough material to make enough mirror to concentrate sunlight at 80 AU out (1/1600 the sunlight!). It might be best to see some bots making fully equipped living space on the Moon and Mercury before we try that one. But yes, as a base, Sedna can be seen as providing free passage to a tremendous amount of raw materials for future space intrigues. Wnt (talk) 21:19, 17 March 2018 (UTC)
1/6400 the sunlight at 80 AU, ~1/875,000 at aphelion... (talk) 02:46, 18 March 2018 (UTC)
To build on the basic point already expressed, but not fully explained: in space, objects do not have the same familiar drags on them that they do on earth. Your scenario suggests a hitch-hiker jumping aboard a passing train to get a free ride out to the Oort cloud. A satellite attempting to land on Sedna would have to match Sedna's speed (i.e. the hitch-hiker would have to run as fast as the train). However, unlike earth-bound hitch-hikers and trains, the satellite and Sedna do not have to worry about friction - they obey Newton's first law of motion in a very different environment than what we experience in everyday life. Once a satellite gets up to the same speed as Sedna, hitch-hiking gives you no benefit as that speed is easily maintained - the satellite will keep going that speed forever (until something else interferes with it). Matt Deres (talk) 13:00, 18 March 2018 (UTC)

Would babies and toddlers need less nap time in the day if they sleep more hours at night?[edit]

If pre-school children all sleep enough hours during the night time, do they really need "nap time" during the day? SSS (talk) 23:48, 16 March 2018 (UTC)

There seems to be a link: " For example, one toddler may sleep 13 hours at night with only some daytime catnapping, while another gets 9 hours at night but takes a solid 2-hour nap each afternoon.". Count Iblis (talk) 02:36, 17 March 2018 (UTC)
Sleep Duration From Infancy to Adolescence: Reference Values and Generational Trends. Alansplodge (talk) 12:33, 17 March 2018 (UTC)
Since retiring, I've drifted back to being polyphasic. --Aspro (talk) 19:38, 17 March 2018 (UTC)
Be aware that the amount and duration of naps and sleep anyone should get is a contentious issue and - at the very least - varies with age. Quick example here. Parents of newborns are inundated with conflicting information, but it's usually formulated the opposite way of the OP. For example, the received wisdom when my child was a newborn (15 years ago) was that having naps improved night-time sleep habits; babies that missed their nap(s) would be too cranky to properly get to sleep at night. That was the theory, anyway. Matt Deres (talk) 16:10, 18 March 2018 (UTC)

March 17[edit]

Continuous, emission and absorption spectrums[edit]

Does anyone know where I can find find the continuous, emission and absorption images for the elements? I am creating a periodic table of the elements and really want to have these added. I found the visible spectrum images on wikimedia, which is fine, and am content on using them. I have looked and searched and found nothing really, except for hydrogen mostly. The kalzium program on Linux distros has the emission and absorption images, but they are small (and the program hasn't been updated for 12 or more years). (talk)

  • You want images? Abductive (reasoning) 06:47, 18 March 2018 (UTC)
  • Are you only interested in simple atomic spectra? Even the helium and rubidium spectra have features in them due to diatomic molecules. In the ultraviolet there may also be a continuum due to ionization. In the microwave region there might be lines due to nuclear spin. Even so, don't expect them to be completely characterized for all different conditions, eg temperature, fluorescent, electric discharge. There are publications with big lists of numbers for frequency and line strength around. There are numerous publications on the topic. If you get something good, you can update User:Graeme Bartlett/spectrum of calcium and User:Graeme Bartlett/spectrum of magnesium! Graeme Bartlett (talk) 07:27, 18 March 2018 (UTC)

March 18[edit]

Does light knock at least some electrons off from any material?[edit]

When light hits a material (any material), can we assume that at least some electrons will be displaced? If we put the material in the dark and illuminate it unevenly, how could we analyze the surface to find spots where light hit? --Doroletho (talk) 14:05, 18 March 2018 (UTC)

First of all, not all light photons will have any effect. They need to be of a high enough energy to do so, which means a high enough frequency - see photoelectric effect and Einstein's first, and Nobel-winning, 1905 paper. (light travels at a constant speed, so its energy depends on its frequency, not like the speed and kinetic energy of a massive particle.)
Secondly, metals and conductors will allow electrons to move freely over their surface. So even if they were displaced, they'd rearrange almost immediately. If the material is a semiconductor though, the effect of the light can be to render that spot conductive. As an insulator, the pattern of electrical charge is fixed in place; first as an even distribution, then as the remainder which wasn't exposed to the light. This is the basis of xerographic photocopying. Andy Dingley (talk) 15:40, 18 March 2018 (UTC)
  • And what instrument is used to analyze the surface of an insulator or semiconductor? --Doroletho (talk) 16:15, 18 March 2018 (UTC)
  • That would depend a bit on the context, and how fine a spatial resolution you want.
Classically, the instrument was the electroscope, mostly the gold leaf electroscope. It's also possible to make an electroscope with a fine wire probe, which can be scanned across an area to 'read' the charge over it. Like most sensitive charge-reading instruments, the reading process is both destructive (it removes the charge that was there) and also needs resetting after each measurement where charge was found. An electronic electrometer is a more modern version of this, and more convenient.
To see the spatial distribution of the charge, xerography can be used. With a semiconductor-coated metal drum (selenium or a semiconductor doped organic polymer) place a constant charge over the whole surface. Then write on it with light (either laser spot or a reflection of the photocopying target), then dust with a fine pigment powder. Light makes the semiconductor conductive, dissipating the charge through the metal drum. The pigment is attracted to the remaining charge, but only in the unexposed areas. Pressing a sheet of paper over this transfers the pigment, giving an image of the remaining charge, and the pigment can be fixed in place by heat fusing it to the paper. Andy Dingley (talk) 17:26, 18 March 2018 (UTC)
Lots of equipment is used to study a material's surface - there's even a name for the entire field of study: surface physics!
Wikipedia has an article, Surface metrology. I have seen commercial equipment for these purposes, called by any of various generic names: "surface metrology station," "laser metrology machine," "profiling machine," "surface roughness meter," ... and so on. For example, you can purchase a "Panasonic Advanced Metrology System Solution" from your local ... place ... that sells semiconductor fabrication test-equipment. Just don't ask how much it costs. As the promotional literature reminds you, "...what does poor quality really cost?"
Other equipment that can be used to study material surface physics of course includes the conventional optical microscope; the electron microscope in all its forms; the atomic force microscope; the Raman spectrometer; the four point probe; and many other unique and specialized types of equipment. Nimur (talk) 17:59, 18 March 2018 (UTC)
See Ionizing radiation for the cut-off for appreciable effects of photon energies on electrons, broadly speaking. Acroterion (talk) 18:02, 18 March 2018 (UTC)
Well, if you use that term, proceed with caution: while it is true that "ionizing radiation" knocks electrons out of their atomic orbit, even "non-ionizing" radiation can add energy to an electron: as Andy linked above, that is called the photoelectric effect. In some materials, like metals and semiconductors, an energized electron has greater electron mobility and may migrate, even if its "parent atom" is not "ionized." If we're not extremely careful with terminology, we can lead to great confusion: when mobile electrons flow in a crystal lattice, we do not usually say that the individual atoms are "ionized." In detailed study of solid-state crystal lattices, we often use the term electron gas or "free electrons" to describe sufficiently-mobile electrons that are not specifically associated with individual nuclei. Importantly: these electrons and their weakly-associated nuclei are not ionized: the total amount of energy is too low to separate the electrons completely. In specific: there is not enough energy to move the electrons to infinite distance from the material lattice. Broadly speaking, ionizing radiation provides exactly enough energy to move the electrons to an infinite distance from their atomic nuclei: this exact quantity of energy is called the ionization potential. Nimur (talk) 18:17, 18 March 2018 (UTC)
Agreed, that's why I qualified my answer. Since the question was about displacement, as opposed to raising an electron's energy level, it seems relevant if the OP isn't familiar with the concept. Acroterion (talk) 18:20, 18 March 2018 (UTC)
Yes, thank you for the clarification. The key distinction is "how far" the electron can be displaced. Nimur (talk) 18:24, 18 March 2018 (UTC)