Wikipedia:Reference desk/Archives/Science/2018 February 4

= February 4 =

3 butterfly species
Hello all, I've been meaning to ask this question for quite a while: I'd like to know 3 rather prolific (as in, literally dozens of them flying around everywhere) species of butterflies I saw in August in and around Nashville, TN -- (1) a small, rather cute one which has similar black markings to the large white, but smaller and is colored a pale yellow-green, like an unripe lemon; (2) also a small one (about 2 inches in wingspan) which is a solid golden-yellow or canary-yellow color with no markings whatsoever, is trapezoidal in shape, and tends to congregate into large groups; and (3) a medium-large black one, similar in coloration and size (slightly bigger than) the mourning cloak, but with disproportionately long forewings (proportions are about the same as for the monarch, but overall size is much smaller), and lacking the distinctive white band around the edges. (I will clarify right now that (3) is not a swallowtail, since it lacks the spurs on the hind wings, and is far too small, and also the tips of the forewings are rounded rather than pointed.) 2601:646:8E01:7E0B:61B1:2817:FCB1:9B27 (talk) 05:38, 4 February 2018 (UTC)
 * 1) Pieris rapae Abductive  (reasoning) 07:16, 4 February 2018 (UTC)
 * 2) Phoebis sennae Abductive  (reasoning) 07:27, 4 February 2018 (UTC)
 * 3) Limenitis arthemis Abductive  (reasoning) 07:34, 4 February 2018 (UTC)
 * Anyway, these are all just guesses from doing Google and Yahoo image searches for 'butterflies of Tennessee'. If you find that I was wrong, please tell me the correct species. Abductive  (reasoning) 07:37, 4 February 2018 (UTC)
 * Well, you got at least 2 of the 3 right -- #2 is definitely right, and #3 is probably right (the shape is right, and the coloration I observed was intermediate between the 2 at the top of the page). I have my doubts about #1, though -- the shape is right, but the ones I saw were more vividly yellow-green, and the black markings were darker (maybe the local variety is more vividly colored?)  Anyway, I'm not an expert on this subject, and I don't want to search the images myself because I would inevitably come across images of swallowtail butterflies (as like as not on high magnification, too), and I don't want to traumatize myself in this way (I'm OK with many butterfly species including all of the above 3, but swallowtails creep me out!)  Thanks! 2601:646:8E01:7E0B:61B1:2817:FCB1:9B27 (talk) 09:50, 4 February 2018 (UTC)
 * Oh, BTW, on second thought, could #1 have been Statira sulphurs? Or are they not found in the Nashville area?  (Of course, the ones shown at the top of the page are too brightly yellow, whereas the ones I saw were paler and with a more greenish hue, but the markings are just about right.) 2601:646:8E01:7E0B:61B1:2817:FCB1:9B27 (talk) 09:55, 4 February 2018 (UTC)
 * Limenitis arthemis comes in a number of subspecies with wildly different colorations. In general, one should not rely overmuch on color when identifying species. Abductive  (reasoning) 13:48, 4 February 2018 (UTC)

What's the highest voltage a closed circuit of D or 9 volt batteries in series could cause for ≥1 second?
Doesn't have to be exact, even an order of magnitude or lower or upper bound is still better than nothing. What would happen to the system? (i.e. terminals heating to X Kelvin, thousands of batteries exploding..) Sagittarian Milky Way (talk) 06:53, 4 February 2018 (UTC)


 * Are you connecting cells in series to create a high voltage, or are you asking about the highest current? The latter depends on the internal resistance of the cells, and a modern Lithium-ion battery can acieve hundreds of amps.   Dbfirs  07:38, 4 February 2018 (UTC)


 * In https://www.youtube.com/watch?v=8hwLHdBTQ7s they got 2000V. I would not recommend the safety precautions seen there, as a current from a 9V battery is enough to kill a person. In another similar video, the spark melted the wire they used. If even more were put in series a spark break down, or corona discharge becomes much more likely. Graeme Bartlett (talk) 10:51, 4 February 2018 (UTC)


 * Impossible to say without more details. The internal EMF of each battery is 9V, same as ever.  The voltage at the terminals depends on the potential divider effect of the battery's internal resistance and the outside load. This will be less than the EMF, and if the battery is depleted its internal resistance increases so that less will appear across the load (this is why dry cell batteries "lose their voltage" when flattened).
 * If you series connect a hundred of these, you get 9V × 100 of EMF, somewhat less as voltage (you're probably using second-hand half-flat batteries anyway). The current will be identical to the current of a single shorted 9V battery. For a PP3, this isn't much - the PP3 design is not a high current battery. The power is high, because it will be the product of I × V and however many batteries you have.   If you short the terminals of your kilovolt battery, there will be arcing and heated wire. However each individual battery will barely be affected - no more than if it were shorted individually. So no, the batteries (PP3s anyway) wouldn't "explode".  D cells?  Bit more.   NiMH or LiPo?   I'd want a blast shield and wouldn't have my hands anywhere near it.
 * The Zamboni pile, used for early electrical experiments, the Oxford bell and 1940s IR night-vision goggles, was a similar battery. Lots of cells. Lots of voltage, very little current. Andy Dingley (talk) 11:19, 4 February 2018 (UTC)


 * This question is ill-conceived. Perhaps you meant the "highest current" rather than the "highest voltage." If I short circuit a cell or battery, I will use a large conductor of copper and the voltage will be extremely low. Would you like .001 volt? If that is too high, I will use a larger conductor and it will be less than .000001 volt. .Edison (talk) 22:31, 4 February 2018 (UTC)

Does soapy water kill my silverfish?
I sometimes find dead silverfish in the kitchen sink after I've washed my hands with a pretty mild kind of soap actually (Marseille soap). I would like to avoid killing my pet silverfish as I find those little guys cute and harmless. So could it be soapy water? It doesn't happen very often, though. But I'd like to avoid it happening at all. Thanks. Basemetal 08:35, 4 February 2018 (UTC)
 * Aren't they simply drowning in the water? (They are of course insects, not fish.) Silverfish are considered household pests, due to their consumption and destruction of property [sic], and contamination of food.--Shantavira|feed me 09:24, 4 February 2018 (UTC)
 * They're probably drowning. Adding soap lowers the surface tension of the water, making it more dangerous to small creatures. PiusImpavidus (talk) 09:36, 4 February 2018 (UTC)
 * Thanks guys. Poor guys. I'll rinse the sink every time then. Gotta do whatcha gotta do. Basemetal  12:37, 4 February 2018 (UTC)
 * You need not feel sympathy for silverfish. They certainly feel none for you. ←Baseball Bugs What's up, Doc? carrots→ 14:15, 4 February 2018 (UTC)
 * You don't want to apply that logic to every cell of someone's body separately :) . Count Iblis (talk) 22:01, 4 February 2018 (UTC)
 * Although they are not known to carry diseases or to bite and are nontoxic if inadvertently ingested, they can make holes in clothes (if they manage to get into drawers or bin). — Paleo  Neonate  – 18:39, 4 February 2018 (UTC)
 * Our cat likes to eat any stray insects it finds, including silverfish, and with no apparent harm. ←Baseball Bugs What's up, Doc? carrots→ 22:29, 4 February 2018 (UTC)
 * No harm to the cat or the insects? Richerman  (talk) 22:52, 4 February 2018 (UTC)
 * To the cat. I can't say the same for the insects. ←Baseball Bugs What's up, Doc? carrots→ 23:10, 4 February 2018 (UTC)
 * The Respiratory system of insects is basically breathing like human skin and it extends this breathing surface with pores and a tracheal trunk system that makes up a inside skin like lungs but much more primitive. Soap is famously able to cover up surfaces like nothing else. Even better than oil on water. It cleans textiles basically by separating everything from everything and then flooding away the loose parts. Soap even manages to encapsulate air in bubbles - in your bath as thick layer of stable foam or for your children to blow flying Bubbles of air. Because soap can cover surfaces so very well it is deadly for insects because it covers up their breathing skin even inside the smallest pores and trunks and thus suffocates the insect, slug or spider. --Kharon (talk) 00:51, 5 February 2018 (UTC)
 * Sorry, but that's nonsense., Human skin doesn't breathe and insects don't have any skin so it can't be extended with pores. Insects have an exoskeleton with spiracles that allow the oxygen to get to the internal respiratory system. Richerman  (talk) 01:34, 5 February 2018 (UTC)
 * Cutaneous respiration all wrong? --Kharon (talk) 01:49, 5 February 2018 (UTC)
 * OK, there is tiny amount, 1-2% in humans, but how does that relate to insects with an exoskeleton? What is the "breathing surface" extended with pores?  Richerman  (talk) 07:06, 5 February 2018 (UTC)
 * I'd second the "nonsense" description here. Insects are chitinous, impermeable and rely on spiracles for the passage of gas to their internal respiratory organs - which could be book lungs in the case of spiders. It's well recognised that they can survive immersion because surface tension keeps the tiny spiracles free of water, but that if you use detergents to lower this, then they may drown.
 * Without having any sources to hand to back this up, I'd be surprised if cutaneous respiration is at all important in most insects. Andy Dingley (talk) 10:46, 5 February 2018 (UTC)
 * There is some confusion here because the tracheae (tubes) going into the body from the spiracles are ectodermal in developmental origin (i.e. homologous with the exoskeleton, the "skin" covering the body). So, just like the rest of the exoskeleton, the surface is moulted. The tracheae also include chitinous structures (important to keep them open). Now, whether you call gas exchange across the walls of these tracheae "cutaneous" is to an extent then a matter just of definition what constitutes skin, but convention is not to call it cutaneous. Some aquatic insects have other structures for gas exchange, including anal gills and external gills. And smaller insects, such as most springtails, can just use gas exchange across the normal epidermis: they need no tracheae. These, then are examples of cutaneous respiration in insects. But silverfish do have tracheae. Jmchutchinson (talk) 19:51, 5 February 2018 (UTC)

Is your lung capacity when you're standing greater than when you're sitting?
Is your lung capacity when you're standing greater than when you're sitting? I don't really see why that would be the case, but then why do singers always stand when they are about to start singing (both soloists and choirs)? Thanks. Basemetal 12:48, 4 February 2018 (UTC)


 * See The effect of standing and sitting postures on breathing in brass players - I'm not really sure that I understand the conclusion, but it seems to be saying maybe - but it depends of the angle of the seat. Alansplodge (talk) 13:12, 4 February 2018 (UTC)
 * Yes, according to spirometer testing. Abductive  (reasoning) 13:52, 4 February 2018 (UTC)
 * If walking is involved, even light walking is better than sitting to promote breathing. — Paleo  Neonate  – 18:41, 4 February 2018 (UTC)

Because to control your breathing properly you use your diaphragm and stomach muscles. You can't control them as well when you're sitting because the abdomen is compressed and there is less space for the diaphragm to drop into the stomach area - especially if you are overweight. Richerman (talk) 23:04, 4 February 2018 (UTC)