Wikipedia:Reference desk/Archives/Science/2017 October 23

= October 23 =

Do old farts dream of flying insects?
I want to know, outside of Germany, are the flying insects disappearing? Do old people remember there being more flying insects in their youth than there are today? 110.22.20.252 (talk) 03:54, 23 October 2017 (UTC)


 * Yes. Bugs are declining. http://www.telegraph.co.uk/science/2017/08/26/windscreen-phenomenon-car-no-longer-covered-dead-insects/ 196.213.35.146 (talk) 07:31, 23 October 2017 (UTC)


 * I assume you excluded Germany because you've already seen this: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185809 196.213.35.146 (talk) 08:28, 23 October 2017 (UTC)


 * Given the huge increase in vehicular traffic and the general increase in speed it should come as no surprise that there will be a decrease in flying insects. I'm in my 7th decade and I remember in the English countryside when you would look up if a car was approaching, and you could sit at the roadside, the A30, than a major trunk road, and write down vehicle registration numbers (for later sorting and scrutiny) with sometimes 10 or 15 minutes between vehicles. Ah, those days. Richard Avery (talk) 14:29, 23 October 2017 (UTC)
 * In case it's not clear: the decline is not due to vehicle use per se, that's just how some people notice the fact. The decline in flying insects is associated with pesticide use, habitat loss, habitat degradation, habitat fragmentation, and climate change. SemanticMantis (talk) 14:53, 23 October 2017 (UTC)


 * OP and interested parties should look through the first few paragraphs of that paper, and the first ~30 or so references, many of which document the decline of flying insects in other parts of the world. It's not just Germany, it's fairly widespread around the world. SemanticMantis (talk) 14:53, 23 October 2017 (UTC)
 * Notwithstanding the risibility potential of malodorousness heralded by audible signal due to sudden decompression of postprandial gaseous abdominal distension, this involuntary occurrence is neither a respectful nor a unique designator of persons of advanced maturity, for whom such usage as that in the heading should be deprecated. Blooteuth (talk) 15:52, 23 October 2017 (UTC)


 * So, if the spiders can't eat as many insects as they were used to will they turn on us? :)  .  Count Iblis (talk) 22:32, 23 October 2017 (UTC)


 * I've personally killed some 500 box elder bugs in my house this fall (one 30 seconds ago), so I have to think human population has an effect. StuRat (talk) 23:40, 23 October 2017 (UTC)

"Fun science" for kids using a laser pointer
What "fun science" can I demonstrate to kids, about 10 to 14 years old, using a red (650nm) laser pointer and common household objects and substances? Roger (Dodger67) (talk) 10:22, 23 October 2017 (UTC)


 * I always thought prisms were cool. Refraction demonstrations maybe? 196.213.35.146 (talk) 10:44, 23 October 2017 (UTC)
 * Diffraction has a demonstration using a red laser. 196.213.35.146 (talk) 10:49, 23 October 2017 (UTC)
 * Before you switch the laser on, ask them what they expect the beam itself to look like. Then show them it's invisible when passing through air.  Cue discussion about Star Wars physics?  Then make the beam visible by producing smoke in its path, or splashing some flour or whatever.
 * Try diffracting the beam through an empty drinking glass by pointing it to the glass off-centre, and mark where the beam lands on a sheet of vertical paper. Test what happens when you fill the glass with water.
 * Have the students predict what colour the spot will appear when the laser is shone on white, black, red, and green objects.
 * Adrian J. Hunter(talk•contribs) 10:58, 23 October 2017 (UTC)


 * I have a handy gadget, which started out as expensive school kit but can now be made at home with a few bucks on eBay. A small plastic box to hold the batteries and a switch, with a red laser module mounted in the side of it. But rather than the usual laser pointer, this has a line lens on it, to give a vertical plane of light, relative to the box base.
 * The advantage is that you can place this on a sheet of paper and demonstrate mirrors, prisms, lenses etc. and because the light is a plane rather than a line, it's visible as a path right across the paper. It makes ray tracing far simpler.
 * A purple laser also shows interesting fluorescence effects, on materials like hardwood, uranium glass and the usual fabrics washed in optical brighteners. Andy Dingley (talk) 11:39, 23 October 2017 (UTC)


 * This has some suggestions. -- Jayron 32 11:56, 23 October 2017 (UTC)


 * One quick thing they might find interesting is to learn that their skin is somewhat transparent. Turn the lights out at night, and have them hold up their hand, then shine the laser pointer through the webbing between the thumb and the rest.  The red light travels well through thin skin, so they should see a nice red glow on the other side.  I would insist on handling the laser pointer myself, though, so they can't shine it in each other's eyes, potentially causing damage.  If this has to be done during the day, use a darkened room or even put hand under a box.  (You might be able to see some red light shine through in full light, but it won't be nearly as impressive.)
 * You could use this as a talking point to lead into how we are even more transparent to other types of radiation. Also, if your kids have a mixture of skin colors, they might notice that dark-skinned people are less transparent to light.  This can lead to a discussion of melanin and how it evolved to protect from UV light, and how this also limits vitamin D production from sunlight, so isn't as prevalent in places with little sunlight.  See Vitamin_D.  StuRat (talk) 17:47, 23 October 2017 (UTC)
 * My apologies if it's already been mentioned, but I always thought the laser pouring water experiment was cool, it simulates the total inner reflection which explains how fiber optics work. Anywho the video is here, enjoy! Drewmutt ( ^ᴥ^ ) talk  00:11, 24 October 2017 (UTC)
 * P.S. Depending on how intense you're lil' guys are there's some easy Double-slit experiments you can do at home to demonstrate quantum mechanics. It's easy to do and the instructions are here. Drewmutt ( ^ᴥ^ ) talk


 * Please teach laser safety first. -Arch dude (talk) 02:23, 24 October 2017 (UTC)
 * No, don't try to teach laser safety. It's far too complicated. Instead, limit all exposure to devices with a strongly divergent beam that are inherently eye-safe. Don't have anything around that you can't safely catch an eyeful of, because it _is_ going to happen.  Andy Dingley (talk) 15:33, 24 October 2017 (UTC)  (using class 4s since thirty-odd years ago)


 * This is why I suggested that only the adult should actually handle the laser. Teaching laser safety is fine, but I wouldn't trust kids with lasers any more than I would trust them with guns (and I don't live in a red state, so we don't have any UZI-packing 9-year-old girls: ) . StuRat (talk) 16:14, 24 October 2017 (UTC)


 * my daugther (aged 14 then) made a Michelson interferometer using a laser, some fixed mirrors, a half-silvered beam splitter, and one mirror that moved using a piezo element. the cool part was that she could demonstrate that the diffraction pattern varied as the piezo moved, showing that she could measure movements down to a few percent of one wavelength of red light (about 10 nm). Her piezo element was the driver from the inside of a buzzer. iI cost about a dollar. she drove ti with a 9-volt battery and a potentiometer. the only expensive part was the half-silvered mirror. -Arch dude (talk) 02:23, 24 October 2017 (UTC)


 * Thanks everyone for the great ideas. I'll certainly keep safety the first priority. The laser I'm using is a "Class III" 5 mW at 650nm. Roger (Dodger67) (talk) 18:59, 24 October 2017 (UTC)

Reason for large difference in pyrethrin solubility due to a methyl group
In the chemistry section of the pyrethrin page Cinerin II and Jasmolin II are related compounds which differ by the addition of a single methyl group yet Jasmolin II has >7,000x the solubility in water. What accounts for this difference? The methyl group is not polar, if anything I would expect a longer carbon chain to reduce solubility in water not increase it. 208.90.213.186 (talk) 21:30, 23 October 2017 (UTC)


 * I'm afraid this rickety structure is unreliable. The article cites PubChem for each compound.  One of them doesn't have solubility listed.  The other credits solubility to a software tool that has since been messed with at the EPA site.  I think it actually still exists  but applying it might be a goose chase - you're welcome to download it and see what you get.  I should note despite a complaint last week, PubChem still says "the atomic weight of chlorine is 70.9..." at .  The great thing about replacing human writers with machines is that the machines can do no wrong. Wnt (talk) 22:46, 25 October 2017 (UTC)


 * OK so it's just made up then. What's wrong with the molar mass of chlorine listed as 70.9? The PubChem page seems clear that it is the diatomic gas. 208.90.213.186 (talk) 22:01, 26 October 2017 (UTC)

Gull intelligence
Is there any research on the cognitive abilities of seagulls? About how well do they compare to corvids and other famously smart birds? My impression is that they're fairly smart, if not corvid level. For example, they can apparently learn to recognize and open food packaging. 2607:F720:F00:4846:1470:AFDA:7A5F:98B5 (talk) 22:00, 23 October 2017 (UTC)


 * Unfortunately, our resident seagull expert,, seems to have retired. You might leave him a note on his talk page, though, in case he returns. StuRat (talk) 22:17, 23 October 2017 (UTC)


 * One way to compare animal intelligence is the mirror test. StuRat (talk) 23:43, 23 October 2017 (UTC)
 * Anecdata: I've often seen gulls trying to attack their reflections, so they evidently don't pass the mirror test. 169.228.159.252 (talk) 03:09, 24 October 2017 (UTC)


 * Not necessarily. They might figure it out, given time.  Heck, a person seeing their reflection in a mirror in an unfamiliar, darkened room might be startled, until they figure it out. StuRat (talk) 03:16, 24 October 2017 (UTC)


 * Maybe they're expressing angst. InedibleHulk (talk) 03:19, 24 October 2017 (UTC)


 * Seagulls do routinely drop shelled items to feed, there are many videos at youtube. But other than be aggressive and trying to eat anything?  I can find no evidence of tool use, co-operative behavior, or cleverness at picked locks.  Of course that's absence of evidence. μηδείς (talk) 02:20, 24 October 2017 (UTC)


 * Incidentally, they may not actually recognize food packaging. There could be several other explanations for why they open them:


 * 1) The see food through clear packaging.


 * 2) They smell food through the packaging.


 * 3) They just open similar packaging, on the hope that it contains food. The test here would be if they open non-food packaging of the same size and shape.  If so, that means they just try them all. StuRat (talk) 02:55, 24 October 2017 (UTC)


 * That's a fixed action pattern which is the opposite of intelligence. It serves the gull well often enough that it's an evolutionarily stable behavior. The same can be said of Sand Wasp reproduction.  Again, I am not saying there's evidence gulls are stupid.  But "they just try them all" is no evidence of their intelligence. μηδείς (talk) 05:48, 24 October 2017 (UTC)


 * Yes, and we need to avoid anthropomorphization. An example I like to use is that if a human community has one well dry up, they may move closer to the remaining working well, using their intelligence.  A plant will also "move" closer to it's one remaining water source, in that roots and stems nearby will enlarge while roots and stems further away will whither, but this doesn't mean any intelligence was involved. StuRat (talk) 16:24, 24 October 2017 (UTC)


 * There's also no stupidity involved when a sunflower "stares" at its photons. Deep down, I think most of us know this, but many still insist these dolts put on the glasses. Even if intended as a public relations boost, not UV protection, the whole altruistic idea is based on a misconception. They don't give a f**ge about us, whether farmed like docile cattle or growing free and wild in a ditch somewhere. We would be in a sorry state without their essential oil. We can't shake their hands, pat their backs or kiss their feet, but can at least not (physically) disturb them while they're busy doing the job we couldn't do as well and would rather not at all. InedibleHulk (talk) 03:47, 25 October 2017 (UTC)


 * I'd still like to try my idea of placing small solar panels on sunflowers, to let them do the Sun tracking for us. Who needs expensive machinery for that ? StuRat (talk) 03:53, 25 October 2017 (UTC)
 * Hardly anyone! InedibleHulk (talk) 04:16, 25 October 2017 (UTC)


 * Bird intelligence applies to gulls, loosely. InedibleHulk (talk) 03:56, 25 October 2017 (UTC)