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September 27

Plutonium density

According to the article allotropes of plutonium, the least dense phase is the δ phase, and it has a face centered-cubic structure. But a fcc structure is one of the two most dense packings possible, the other being hexagonal close-packing. How is it that the most dense packing structure gives the least dense allotrope? 202.155.85.18 (talk) 06:39, 27 September 2018 (UTC)

• The article matches the refs, even though it seems extraordinary. (A negative thermal expansion coefficient for a crystal? Come on...) Ref #2 lists (p. 294) your remark as "unusual property" #5 and ascribes it to nonstandard behavior of the 5f electrons (p.296 and following give an explanation but I find it hard to follow); in other terms, the "rigid spheres with a constant atomic radius" model is too wrong to apply it here. Tigraan^{Click here to contact me} 07:18, 27 September 2018 (UTC)

Hmmmm...actually that makes a lot of sense. The Goldschmidt correction for actinide series elements is probably much larger due to the lanthanide contraction, so as the coordination number is increased going to more and more close packed structures, the metallic radius increase is so great it leads to overall lower densities. Thanks! 202.155.85.18 (talk) 07:26, 27 September 2018 (UTC)

I don't know what the bloody hell you two are on about but that was great. It almost made me want to follow the links. (I always found physical chemistry banal). — Preceding unsigned comment added by Greglocock (talk • contribs) 09:56, 27 September 2018 (UTC)

Exoworlds with glowing vegetation

I believe that exoworlds with colorful glowing plants covering much of the world exist like Pandora from Avatar. What do you guys think? Glowing plants are obviously very uncommon on Earth with the most common species being sea-dwelling kelp. PlanetStar 21:11, 27 September 2018 (UTC)

See article Bioluminescence for the glowing and its functions. Contrary to your assumption the Abyssal plains (depths below 3,000m) actually cover more than 50% of the Earth’s surface! Since there is hardly any sunlight reaching these deeps - even the Macropinna microstoma, that uses giant eyes pointing upwards to detect prey against the light from the surface, prefers much higher zones around 1000m depth - and Bioluminescence is pretty common in these deeps, we actually have masses of glowing lifeforms here at "home". Just no "jungles" full of it because all food sources are way to scars that deep, to feed so much life.

One interesting revelation, since you cite the Movie Avatar as reference, is that the Director of that movie, James Cameron, actually became an expert on deep-sea exploration and thus certainly saw lots of Bioluminescence down there himself, which probably inspired him to add this to his computer generated jungle world Pandora and its biosphere. --Kharon (talk) 22:12, 27 September 2018 (UTC)

James Cameron seeing bioluminescent lifeforms deep below the ocean's surface inspired him to generate jungle of bioluminescent plants, both on land and underwater in the Avatar movie, which in turn inspired me to ask question about the real life existance of such a jungle on alien worlds by watching it. Although bioluminescent plants and animals are abundant deep in the ocean, why is bioluminescence so uncommon on land plants and animals? Isn't Earth unusual for a life-bearing planet to not have land bioluminescence in abundance? PlanetStar 21:18, 28 September 2018 (UTC)

In most cases bioluminescence is rather faint. There are some "surface" plants like Schistostega pennata where bioluminescence seems to have a benefit but our earth vegetation actually thrives great without it. Avatar is just a fantasy movie. You certainly will not find flying mountains anywhere in our universe for example. But they look spectacular of course - like bioluminescent jungles or elegant 3.5 meters high blue-coloured humanoids with huge shiny eyes do. Again, it's a movie. Don't read too much into it, especially when it's from the Sci-fi or fantasy genre. --Kharon (talk) 12:28, 29 September 2018 (UTC)

Isn't Earth unusual for a life-bearing planet to not have land bioluminescence in abundance? How could we know, since we've not discovered life anywhere else yet? —PaleoNeonate – 19:37, 30 September 2018 (UTC)

Fireflies put on an impressive display, but a fairly dim one; nature can be stingy. (pure speculation:) Still, I'm thinking that the abyssal plain is always dark, but the Earth, even at night, is often moonlit. Perhaps a planet without a moon would encourage more investment in bioluminescence? Another issue for plants is that their potential mates can neither see the display nor respond to it; they could signal to pollinators but other methods might be cheaper. But, what if another planet developed somewhat mobile plants with some degree of color vision? In truth, of course, we know nothing at all about other biospheres, nor can we predict them with any confidence. Wnt (talk) 00:38, 30 September 2018 (UTC)

I know Pandoran jungles seem fantastical, well, who knows, alien biospheres can be fantastical too. From my point of view, why isn't the Earth covered in Pandora-like glowing jungles and forests on land, while from Cameron's POV why isn't plants glowing deep underwater cover much of the land too? Maybe it's just the way the Earth's evolution went. My sister said had evolution gone in a slightly different direction, we would possibly see land forests/jungles of glowing plants. Of course it's far more likely to see these than flying mountains. Sci-fi never even look into rocks that fly, at least from my point of thought. PlanetStar 03:02, 30 September 2018 (UTC)

If you think rocks don't fly, watch a volcanic eruption sometime. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:23, 30 September 2018 (UTC)

Uuuuhhh, that's right! I could now say rocks don't have feathery wings and aren't self-aware. PlanetStar 19:29, 30 September 2018 (UTC)

Gecko in or out of house?

Background: I live in a large house in Algeria, where daily outside temperatures are typically from ~ 17 to ~ 27 C. There are cats in one room of the house (don't ask). The population of flies in the house seems fairly minimal to me. I see adult geckos outside the house, and occasionally find baby ones inside (not in the room which has cats, but they could get under the door). I typically transfer the babies outside, in the basis that they're more likely to live long and happy lives there.

My question: am I right, or am I just providing food for various predators? I realise refdeskers can't calculate the odds of a particular gecko being stood on / eaten by cats / freezing to death, but in general terms, is there a scientific basis for thinking they're better off in or out? 105.235.137.66 (talk) 21:12, 27 September 2018 (UTC)

It's typically 17-27 but they might freeze to death? I assume this is not the low desert? Sagittarian Milky Way (talk) 00:11, 28 September 2018 (UTC)

How does one freeze at 17C?--Jayron32 00:30, 28 September 2018 (UTC)

OP says "Daily outside temperatures are typically from ~ 17 to ~ 27 C".

Our article says "on the steppes of the High Plateaus winter temperatures hover only a few degrees above freezing". Rojomoke (talk) 04:46, 28 September 2018 (UTC)

The IP geolocates to Algiers, which has Csa sub-climate classification. Regarding the original question, it is essentially a matter of opinion, which this reference desk doesn't provide (stop laughing!). That being said, I'd be inclined to let nature take its course; if the geckos manage to find enough bugs to eat in your house -- great! Otherwise, they just might leave the way they came in (or end up being a nutritious cat snack). In many places it is considered good luck to have a gecko in the house (Hawaii, Indonesia, etc.). —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 06:00, 28 September 2018 (UTC)

Thanks, 2606, for not completely ignoring the question. Re: temperatures, I should have specified currently (could also have specified that dying of cold does not necessarily require temperatures literally below freezing). Re: opinion, I was hoping for (e.g.) some animal welfare society guidelines, which would be based on expert knowledge. All I find online is about caring for captive gecks. 105.235.137.247 (talk) 07:09, 28 September 2018 (UTC)

I never heard of "geckos" before. I only came across the word in a description of a browser using Chrome/Internet Explorer where it says "like gecko". What does that mean? 86.131.233.235 (talk) 09:39, 28 September 2018 (UTC)

See Gecko. Or watch some Geico TV commercials. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:08, 28 September 2018 (UTC)

While it's possible that your decision to take a pro-active vs. laissez-faire approach may have a massive impact on any one gecko (one may, as you fear, be snatched up by a predator instantly), as a probabilistic matter it is unlikely that your habit of removing them has a substantial net effect one way or another (that is, if you remove a hundred of them in a given year, probably close to the same number will meet their end shortly after their encounter with you). Young geckos, like most juvenile lizards, have a higher ounce-to-ounce metabolism than adults as they develop and specimens of almost all species likely to be in your house utilize a lot of energy in movement. Consequently, those individuals from species which have not developed a mechanism for storing energy in fat reserves (there are numerous of these, such as the fat-tailed gecko and the leopard gecko) need to eat fairly consistently, and they rely very much upon the conditions of their ecological niche for predation. This means that most geckos who end up in your house, particularly the young ones, will quickly begin to feel the pangs of hunger. That said, while there may be the occasional home which has features that make it likely to confuse a gecko guest such that they become trapped, by and large they will not have much difficulty in finding their way out again when circumstances prompt them to--so provided there are no environmental hazards inside the house (of the feline variety or otherwise), they should be fine if you leave them be.

Of course, this all assumes that the effort you are going to exert is limited to walking them to the door. If you really want to give the best possible chances to your reptilian boarders, you should identify the exact species, learn which flora provide them the best hunting and defense opportunities and deliver them to the nearest acceptable specimen. Most adult geckos will also be more than happy to accept mealworms or crickets, if you can find a supplier that provides them and have the patience to set the gecko up in a vivarium for a while--if you were really dedicated to giving them a leg up on their way out the door. Sorry I can't find a suitable source for all of this; I did look but couldn't find anything particularly on point--this is just a summary of various details I happen to know regarding lizard physiology and ethology. Snow ^{let's rap} 09:45, 28 September 2018 (UTC)

Thanks, that's useful. To clarify, when you say if you remove a hundred of them in a given year, probably close to the same number will meet their end shortly after their encounter with you, do you mean just that most baby geckos don't survive long, or the ones I find are most likely already in bad shape? I'll try to identify the next one, in case I can do better by him. 105.235.137.247 (talk) 10:38, 28 September 2018 (UTC)

Well, survival rates will vary by species and location, but what I meant is that over a large enough sample size, your decision to remove them or not remove probably will not have a significant impact on the longevity of the Gecko's in that particular group, collectively. That is, you will probably not have a big impact on their fortunes (on average) whichever approach you land on (again, assuming you are just taking the ones you remove to the door).

Incidentally, there is another consideration I didn't think to mention before that I'll emphasize now; as a cat owner, you may wish to remove the geckos just to reduce the likelihood that they may come into contact with your feline roomates; lizards oftentimes carry parasites, some of which your kitties could possibly contract from ingestion. Small mammals are more likely to operate as this sort of vector than reptiles, but better safe than sorry. It's also a really bad way to go for the lizard; domestic cats typically do not hunt out of hunger, if they are owned and properly fed, so they drag the affair out to excruciating length before eating just bits. As someone who has done some wildlife rehabilitation, I can tell you that there's little that's more difficult to deal with than an animal a cat had a hold of for half an hour--but refused to finish off, because it was entertained by the movement. Geckos probably go a bit faster from abdominal puncture wounds, because of their size relative to a cat, but still, a miserable end. And sure, no problem--happy to help. :) If you need assistance in identifying the species, let us know, and feel free to ping me. Snow ^{let's rap} 10:54, 28 September 2018 (UTC)

Good points. The cats are completely inept hunters, which would probably prolong things even if they didn't want to. As long as I'm not clearly sending the little guys to their deaths, I think I'll continue with my transfer policy, while trying to find an optimal drop-off point. 105.235.137.247 (talk) 15:26, 28 September 2018 (UTC)

If you've got little geckos slithering their way into your house, what other, smaller creatures might be invading also? ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:02, 28 September 2018 (UTC)

I think that carrying capacity is the relevant concept here. It is very difficult to predict, short term, the effect of releasing a few extra geckos into a wild population. They might, after all, be momentarily low in numbers for some reason, so that the introduction of new blood helps them to recover faster. Or, they might be near a population crash where a few extra mouths help them all to starve. But if you come back in fifty or a hundred years, the number of geckos each year will follow some random pattern that will depend in no significant way at all on how many you released. What this means is that for every gecko you lovingly feed, nurture, and defend as it makes its way into the wild, there is another gecko which is pushed aside by your newcomer and crawls off to some unwatched corner of the wild to die.

The situation in your house may be the same; in that you may be relatively inefficient at catching geckos so that the "predation" imposed by your good intentions (plus the doorway to the room full of cats) actually has little real influence on the total population. Much likea properly managed hunting or fishing season in the wild would be. On the other hand, you certainly could catch every single last gecko and put up a Great Wall of Trump to keep out any future invaders, and leave the stray bits of kitty kibble to be dealt with solely by some other member of the ecosystem (bacteria, mold, cockroaches, or Roomba). Then, there would genuinely be some lost gecko-hours of home enjoyment lost forever to history.

I think the reason why this seems surprising to our expectations is that with humans there is a culture. We expect that if there are more people, eventually they discover plows, domesticate plants and animals, or do genetic engineering trying to improve the carrying capacity of the environment, also they may actually limit their own fecundity, all of which means that increasing their numbers now doesn't automatically guarantee exterminating the same number in the future. (Though it scarcely rules it out either) Wnt (talk) 19:39, 28 September 2018 (UTC)

Interesting! In this particular case, geckos here suffer from religious persecution (not every day you get to write that), so perhaps carrying capacity is not the limiting factor. 105.235.137.251 (talk) 22:27, 28 September 2018 (UTC)

I couldn't help but take that bait: [1][2][3][4][5]. I didn't come to any strong conclusions, but it's interesting. Wnt (talk) 23:27, 28 September 2018 (UTC)

Mainly this. There may be a pragmatic origin related to e.g. parasites, but basically it's superstition. 105.235.137.251 (talk) 06:17, 29 September 2018 (UTC)

What I was referring to was this sentence in my browser configuration details:

AppleWebKit/537.36/KHTML, like Gecko

I googled the term but there is nothing listed. What does it all mean? 86.131.233.235 (talk) 17:34, 29 September 2018 (UTC)

Gecko (software) is the "browser engine" that displays a document in the web browser, after it has somehow been obtained. It explains at the first article how Apple made its own version in 2001, back when Netscape was a popular browser, but one that took a long time to start up on account of all the "software bloat" it had accumulated. Wnt (talk) 18:26, 29 September 2018 (UTC)

Now I understand why they call it a "search engine". I had always wondered. Thanks. 86.131.233.235 (talk) 18:53, 29 September 2018 (UTC)

September 28

Flexible tubing resistant to ~350 C (660 F)

There's a desoldering tool whose main feature seems to be a piece of silicone tubing which the manufacturer claims can be in contact with the soldering iron. A typical soldering iron temperature is 350-370 °C (~660-700 °F). I figured I could buy some silicone tubing and put it on my cheap desoldering tool but I can't find any that is good up to 350 °C. Is it actually possible? If so, does anyone know how I might find it or alternatively some other small-diameter tubing that's as flexible and heat-resistant? 185.230.100.66 (talk) 03:01, 28 September 2018 (UTC)

Your google fu is weak https://core-electronics.com.au/replacement-tubes-for-professional-silicone-tip-solder-sucker-ss-02.html Greglocock (talk) 04:36, 28 September 2018 (UTC)

Thanks! — Preceding unsigned comment added by 185.230.100.66 (talk) 05:45, 28 September 2018 (UTC)

Solder sucker tips are usually made of PTFE (Teflon) that melts at 327°C. Although our article about Silicone rubber quotes an upper use temperature of 300°C (and an O-ring manufacturer quotes a limit at 450°F=232°C[6]) the "fancy" transparent silicone tube for solder sucking is claimed[7] to be heat resistant to 350°C. The term silicone can cover a large group of Elastomers in which vinyl-methyl-silicone is the central ingredient, with chemical inertness and high temperature resistance attributable to the stability of their Si-O-Si atomic backbone. DroneB (talk) 15:03, 28 September 2018 (UTC)

• There are several factors to take into account, because heating an object has a lot more involved than just temperature. There are also things like thermal conductivity, thermal diffusion, and heat capacity to consider, to name a few. Temperature, for example, you can think of as being a surface quality, because you can only measure it at the surface or extract energy from it at the interface of a surface.

Most polymers (plastics) have low melting temperatures. As far as common polymers go, Teflon, is the highest, although some exotic polymers do exist that reach temps up to 850 degrees F, these are mostly used in the aerospace industry. However, if your polymer is a thermoplastic and not a thermoset, it will melt, but it will melt like glass rather than a crystalline like ice or metal. Before it melts it crosses through the glass transition (T_g), and starts to be come pliable and rubbery. The more you heat the softer it gets, until it crosses the glass melting temperature (T_m). A thermoplastic's damage threshold is often (but not always) lower than the glass transition and much, much lower than the glass-melting temp. Teflon, being a semi-crystalline, is one of those exceptions. It's T_m is 626 degrees F (330 C) while its T_g is -166 F (-110 C). (This is what gives it its combination of rigidity and pliability.) However, above 527 F (275 C) the material begins to lose that rigidity sharply, thus the damage threshold is kept 50--100 degrees lower as a safety margin.

Elastomers (elastic polymers) like silicone are different, because these are usually thermosets, and thus will not melt. Instead, above their damage-threshold safety margin, they begin to burn instead. For high-temp silicone, this will be at around 500 F (260 C), which is the highest temp you can find in a common elastomer. (Although there are some exotic ones like Kalrez that can go higher.) For much higher temps you may need to use a fabric, or even a glass fabric that can get you up over 1000 F (540 C).

Fortunately, this really only applies if you're holding it at that temp for extended periods of time, such as in an oven. In a solder sucker, the plastic only contacts the molten metal for a short time. Because the plastic has poor conductivity and high capacity, it doesn't absorb this heat very fast, so it never actually reaches the temp of the molten metal. (This also keeps the metal from cooling too quickly and hardening on first contact.) So, for intermittent use like this, a plastic or polymer with a lower melting point than the metal can work just fine. Zaereth (talk) 19:34, 28 September 2018 (UTC)

The OP whose IP address is located in the UK posed a question with temperatures primarily in degrees Celsius, the unit used by all countries except the United States, the Bahamas, Belize, the Cayman Islands and Liberia. It would be a courtesy to give answers in the same units rather than imposing a superfluous conversion from a unit of local use in the United States, the Bahamas, Belize, the Cayman Islands and Liberia. DroneB (talk) 22:13, 28 September 2018 (UTC)

Sorry, I will keep that in mind. The OP asked using both, and for that reason it didn't occur to me to convert from the numbers I know by heart. Zaereth (talk) 23:08, 28 September 2018 (UTC)

Courteous behavior is what you do and not just something you think about doing some time in the future. Do you wish anyone to help edit your post with appropriate units? DroneB (talk) 23:59, 28 September 2018 (UTC)

If you wanted me to change my post all you had to do was ask. My time is very limited, but I thank you for the lesson in courtesy and how to deliver it with condescension and equivocation. (Suddenly, I remember why I don't respond here.)Zaereth (talk) 06:05, 29 September 2018 (UTC)

Ref. desk rules differ from Wikipedia mainspace in that I am not allowed to change what another has posted, so I only suggested how and why your post might be edited. Thank you for acting on my suggestion and for all your work here. DroneB (talk) 14:47, 29 September 2018 (UTC)

Actually, here in the U K we are familiar with both scales. The papers will say that temperatures will reach 95° and we all know what that means. If they said they were expected to reach 35° we would have to think about it. — Preceding unsigned comment added by 86.131.233.235 (talk) 19:03, 29 September 2018 (UTC)

On wikipedia, you can just write {{convert|95|°F|°C}} or {{convert|35|°C|°F}}, which will display as "95 °F (35 °C)" or "35 °C (95 °F)" respectively. You state what you have, and the template converts it to the other one automatically. Then we can spend our time more productively, arguing about which to should be the main vs parenthesized units. DMacks (talk) 04:14, 30 September 2018 (UTC)

For what it is worth, I gathered everything I have that is made of silicone -- around a dozen different items. I then applied my soldering iron. At 350/375/400 °C (my normal soldering temperatures) the silicone laughed at me. At 450 °C I was able to make a mark on a cheap scrubbie ( https://www.amazon.com/gp/product/B01MREBZ2V/ ) but not on any of the other items. --Guy Macon (talk) 11:12, 30 September 2018 (UTC)

Yesterday I had a bunch of soldering to do, so I decided to use one of the cheap scrubbies I mentioned above (flat side up) as a soldering mat. I usually solder at 375°C, switching to 350°C for heat sensitive components and 400°C for soldering to heavy ground planes. It worked great. I put a blob of solder on it and heated it to 400°C. When it cooled off it fell right off, and didn't even leave any flux residue. The pad looks like it did when it was new. --Guy Macon (talk) 17:22, 1 October 2018 (UTC)

Antimatter

In space, are there naturally occurring accumulations of antimatter in significant amounts (say, 300 lbs. or more)? 2601:646:8A00:A0B3:19E8:E4E1:14EA:832C (talk) 06:18, 28 September 2018 (UTC)

As far as we know, the answer is no. If they do exist, they must be quite rare. If there were large clumps of antimatter in our universe, these would be expected to sometimes encounter ordinary matter, which would result in colossal explosions. The fact that we haven't seen the signs of large matter-antimatter explosions indicates (at the very least) that any macroscopic accumulations of antimatter must be extremely rare. Dragons flight (talk) 07:15, 28 September 2018 (UTC)

I'm not an expert, but from the sort of explanation given in Chronology of the universe, it is believed that all of space was filled with a nearly homogeneous plasma for quite some time. As such, it is difficult to imagine that nucleosynthesis or subsequent processes would have permitted the assembly of 300-pound lumps of antimatter in the middle of space at random; they should have been annihilated. Every once in a while I read about people hunting for antimatter islands in the cosmos, but my understanding has been they are looking for very large regions (very, very far away) which might be indicative of how the overall asymmetry got started. That said, then there's stuff like this. Dragons flight was correct to take the empirical approach, but I just wanted to heads-up a little on the theoretical aspects. Wnt (talk) 19:24, 28 September 2018 (UTC)

In the very beginning of the Big Bang there was neither matter nor antimatter, but the primordial ingredients for both. It is really a mystery as to why one formed but not the other, but it could have been as simple as the grain of rice that tips the scales. What we do know, and most people don't consider, is that space is not a total vacuum, but is filled with dust and gases; in some places at extremely low pressures and others extremely high. In fact, our local region of space, through which the heliosphere travels, is one of those extremely low-pressure areas compared to the surround galaxy. Even so, far greater vacuums have been created here on Earth than are found in space. According to Chakrabarti, the closest thing you can find to a total vacuum is near the event horizon of a black hole, where matter enters with the speed of light. Thus, it is highly unlikely that any quantities of antimatter exist, and if they do, it would most likely be extragalactic. Zaereth (talk) 22:43, 28 September 2018 (UTC)

Oh yes, by "very, very far" I meant "large Hubble constant". Even so, that antimatter-detecting instrument on the ISS at least seems to be finding something. I think your description of the heliosphere and outer space in general is inaccurate but I don't have the figures to argue it. The asymmetry has something to do with the failure of CT symmetry, so it's probably not just random. Wnt (talk) 23:51, 28 September 2018 (UTC)

Average density in the area of Earth is around 0.25 particles per square centimeter, which is a mixture of neutral atoms (mostly hydrogen and helium) and ions traveling outward from the sun at supersonic speeds. However, at that distance, the gas pressure is not nearly as high as the ram pressure (the inelastic, supersonic column of pressure described a few sections above), which is roughly equivalent to the magnetic or radiation pressure. The pressure gets very high as the flow goes from supersonic to subsonic, forming a shockwave we observe as the bubble of the heliosphere. The shock dissipates the energy until the pressure in the shockwave reaches an equilibrium with the surrounding local interstellar medium (LISM), which has a density of about 0.07 to 0.015 particles per square centimeter, although this tends to be lower than the density in the surrounding local interstellar cloud.

I think it's likely antimatter exists out there, but find it doubtful it does in large quantities within the interstellar medium. (There is an interesting theory that the accelerating expansion of the universe may be powered by a pressure differential between it and the total vacuum that may be outside the universe (where laws like the speed of light may not even apply). It may be entirely possible that gas densities between galaxies are even higher than in certain areas within them, like water whirlpooling around a drain or air in the capture-zone of a fan. Or they may be lower. These are all just hypotheses at this point.) The problem is that the original question is one of cosmology, thus all we have are best guesses. Zaereth (talk) 01:29, 29 September 2018 (UTC)

Our article Local Bubble is somewhat relevant. Long story short: the Solar system and a few nearby stellar systems sit within an irregular bubble whose interstellar medium of gas and dust has around 1/10th of our galaxy's average, caused by one or more nearby supernovas within the last 20 million years. As a formerly active astronomer and science textbooks editor, I concur with Zaereth's initial and subsequent descriptions, which perhaps Wnt initially misread. {The poster formerly known as 87.81.230.195} 90.217.102.65 (talk) 10:11, 29 September 2018 (UTC)

There's a Larry Niven story Flatlander about a planet made of antimatter. Spoiler:

It was as if he'd screamed. I could hear that word echoing from side to side in my skull.

Elephant's booming voice was curiously soft. «Antimatter?»

«Of course. We have no excuse, of course, but you should have realized it at once. Interstellar gas of normal matter had polished the planet's surface with minuscule explosions, had raised the temperature of the protosun beyond any rational estimate, and was causing a truly incredible radiation hazard. Did you not even wonder about these things? You knew that the system was from beyond the galaxy. Humans are supposed to be highly curious, are they not?»

173.228.123.166 (talk) 02:58, 29 September 2018 (UTC)

Hawking radiation

How big must a black hole be in order for its evaporation to create a 20-kiloton explosion? 2601:646:8A00:A0B3:19E8:E4E1:14EA:832C (talk) 06:20, 28 September 2018 (UTC)

Since the blackhole's entire rest mass is released as energy as it evaporates, the mass of the black hole that causes a release of 20kT($8.37\times 10^{13}J$) will be given by $m={\frac {E}{c^{2}}}$ i.e. $9.298\times 10^{-4}kg$. Then we can use the relationship between the Schwartzschild radius and the mass ($r_{s}={\frac {2GM}{c^{2}}}$ where G = 6.674×10⁻¹¹ N·kg^–2·m²) to determine that such a black hole would have a Schwartzschild radius of $1.38\times 10^{-30}m$. 202.155.85.18 (talk) 08:55, 28 September 2018 (UTC)

Thanks! Would it be possible to create such a black hole artificially (e.g. in a particle accelerator), or would the energy requirement be prohibitive? 2601:646:8A00:A0B3:D843:FF23:EE04:4F41 (talk) 11:25, 28 September 2018 (UTC)

Today I learned the largest fossil fuel power plants burn a Hiroshima of energy each in ~2 hours. No wonder there's global warming. Sagittarian Milky Way (talk) 18:45, 28 September 2018 (UTC)

I wasn't talking about the biggest power plant, but about the biggest particle accelerator (or whatever other means there might be of creating black holes artificially). The reason is, there's been a scare a few years back about the possibility the Large Hadron Collider might create a black hole which would then suck in the whole Earth -- which is an impossibility given that small black holes evaporate so fast, but I thought that maybe such a scenario could create the hazard of a nuclear explosion instead? 2601:646:8A00:A0B3:D843:FF23:EE04:4F41 (talk) 09:30, 29 September 2018 (UTC)

If a micro-black hole was created in a particle accelerator, there is no guarentee that it would evaporate, since Hawking radiation is postulated, but not proven. On the other hand, it's totally impossible for a micro-black hole to "suck in the whole Earth". A micro-black hole of a given mass doesn't have any more gravitational pull than any other object of the same mass. In other words, a ~1g micro-black hole such as the one that would give a 20kT blast if it does in fact evaporate, would exert no more gravitational pull on the matter around it than a 5 carat diamond. 2400:D400:9:1268:306:200:0:10B0 (talk) 09:58, 29 September 2018 (UTC)

True, but my question is, would it even be possible to create a 1g black hole in the first place, or would the amount of energy required be too out of this world? 2601:646:8A00:A0B3:D843:FF23:EE04:4F41 (talk) 10:40, 29 September 2018 (UTC)

That's really difficult to say with any degree of accuracy, but we can make a ballpark guess. The compressibility of nuclear matter is very roughly 300MeV based on theoretical calculations [8]. If we wanted to compress a proton into a space smaller than its Schwartzschild radius, we'd be reducing its volume by 38 orders of magnitude. To a first order approximation (and assuming this type of classical mechanical calculation is even valid for this quantum system) that would take around 337 Joules. That's not a prohibitive amount of energy for us to come up with, but it's probably very difficult for us to focus that amount of energy as a compressive force on a single proton. Since the Large Hadron Collider is not some kind of quantum scale diamond vice, it's hard to imagine a situation where a micro-black hole would be created. Maybe where the forces of acceleration on a given particle are so great that it experiences enormous compression on a time scale too short for it to relax through expansion in the dimensions perpendicular to the acceleration. Though when day dreaming about what fantastical properties a subatomic scale black hole might have, it's good to keep in mind that electrons already display many of the properties of a micro-black hole.139.194.67.236 (talk) 12:29, 29 September 2018 (UTC)

My impression is that the black hole electron idea involves a mass and singularity that doesn't fit within the Schwartzschild radius (the position is simply too uncertain!). Yet if it doesn't ... how is it a black hole? Hmmm. I wonder if anyone has tried to model a super-extremal fuzzball (string theory)?? Our article says those have a volume equal to black holes, but are made up of strings, which are quarks. I'm not clear on whether each of the six types of quark has a volume in string form that is proportional... the part about them getting less dense the more they are is also curious ... but if you can take those quarks and somehow shave them down to something with a -1 charge and a mass much less than that of a quark, that would take the game, set and match! Wnt (talk) 00:28, 30 September 2018 (UTC)

Electric-field equivalent of Lenz's law?

I note that the article on Lenz's law states that "the direction of the current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field". This is useful heuristic for getting the sign on the magnetic field right on boundary condition. Is there a corresponding law for electric fields? If so, what is it called? If not, why not? I admit that I might be missing some understanding, here, so comments/help are welcome. Attic Salt (talk) 17:25, 28 September 2018 (UTC)

As there are no magnetic charges and therefore "magnetic" conductors, there is no "Lenz's" law analog for electric field. Ruslik_Zero 18:30, 28 September 2018 (UTC)

Hmm, I guess I was thinking of something different from that. Insofar as magnetic discontinuities are supported by current sheets, for example, at surfaces, I would think that a (possible) electric Lenz's law would involve surface charge -- something consistent with Maxwell's equations and Ohm's law. I just don't quite know how to phrase it or if someone has it named after him/her. Attic Salt (talk) 18:57, 28 September 2018 (UTC)

Two urine streams from pressure

I get the experience when I often lay belly down on the floor or bed and putting pressure on my urethra, it seems that is cause me whenever I pee it usually comes out in two streams or one wide stream rather than one thin stream. Other times when I get away from home and not laying on the floor for hours, I usually pee it out in one solid stream afterwards. Is it true that pressing urethra on the floor or bed causes it to pee it out in two streams? PlanetStar 22:19, 28 September 2018 (UTC)

You should see a doctor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:31, 28 September 2018 (UTC)

LOL, this is a deep male secret that no woman should be permitted to learn, so here goes. ;) Humans do not form vaginal plugs, but wankage is not always entirely traceless. Wnt (talk) 23:54, 28 September 2018 (UTC)

Not funny. Meatal stenosis or narrowing of the opening of the urethra that causes abnormal direction of the urinary stream is commoner among circumcised males due to lack of a protective foreskin. A urologist (whom the OP should consult) may carry out a Voiding cystourethrography (VCUG) test if a physical exam, e.g. using ultrasound, indicates an incorrect urine flow or Urinary tract infection that could put the bladder or kidneys at risk. DroneB (talk) 00:30, 29 September 2018 (UTC)

Semen does get sticky when it congeals, no? Anyway, what you describe sounds like a long-term/medical situation, but what I'm suggesting is an issue that, once understood, is readily attributable, and in any case (dis)solves itself. Wnt (talk) 01:30, 29 September 2018 (UTC)

See Nozzle. Bus stop (talk) 01:13, 29 September 2018 (UTC)

The one reference source more comprehensive than Wikipedia has an article about this.[9] 173.228.123.166 (talk) 04:25, 29 September 2018 (UTC)

Despite the fact that I have pointed out on multiple occasions that no Wikipedia policy or guideline exists against giving medical advice except in the fevered imagination of a few people who do not understand the concept of "disclaimer" -- and that only an idiot pays any attention to medical advice from random strangers on the Internet -- this is a situation where I really think that User:PlanetStar should see a doctor. It doesn't happen to me when I lay down the same way, nobody here has come out and said that it happens to them, and it just might be either [A] something minor but still worth asking a doctor about, or [B] something serious that is just starting to show the first symptoms. (Medical disclaimer.) --Guy Macon (talk) 04:29, 29 September 2018 (UTC)

Yet another off-topic attempt to enforce an imaginary rule that does not appear in any Wikipedia policy or guideline. --Guy Macon (talk) 02:18, 1 October 2018 (UTC)
The following discussion has been closed. Please do not modify it.
Wikipedia:Medical disclaimer is the policy or guideline. ←Baseball Bugs What's up, Doc? carrots→ 08:47, 29 September 2018 (UTC) Even if I accept your dubious claim that a disclaimer is a policy, that page would be a "policy" that utterly fails to say that we cannot give medical advice. The lawyers who wrote the disclaimer were invited to set a policy (which they are allowed to do; see Wikipedia:Office actions) that we are not allowed to give medical advice. They declined to do so. Wikipedia:Medical disclaimer says that when we give medical advice, no warranty is made that the advice is accurate, true, correct, precise, or up-to-date. It doesn't say that we can't give medical advice. It says that when we give medical advice, our advice cannot substitute for the advice of a medical professional. It doesn't say that we can't give medical advice. It says that when we give medical advice, even if our advice is accurate, it may not apply to you or your symptoms. It doesn't say that we can't give medical advice. It says that when we give medical advice, we do not take any responsibility for the results or consequences of any attempt to follow our advice. It doesn't say that we can't give medical advice. It says that when we give medical advice, it should not be construed as an attempt to engage in the practice of medicine. It doesn't say that we can't give medical advice. All of which is lawyer talk saying the same thing I said in plain English above: only an idiot pays any attention to medical advice from random strangers on the Internet. Baseball Bugs, please stop citing imaginary policies. For the pedantic who really want to know what the rules are: some medical advice is forbidden under the general rule prohibiting disruptive comments, but not all medical advice. For example, the following medical advice is allowed: Don't do crystal meth. It will screw up your health. Don't bother asking a doctor if crystal meth is good for you. It isn't. There. I just provided medical advice, and while I did make a point, I did so without being disruptive. There are some who believe that Wikipedia has a policy against giving medical, legal, and business advice, but no such policy or guideline exists except in the fevered imagination of a few people who do not understand the concept of "disclaimer" (If you are about to cite the reference desk guidelines, please read WP:LOCALCON and then show me where the Wikipedia community approved them). Feel free to report my behavior at WP:ANI if you believe that I have violated any Wikipedia policy or guideline. Did I mention that Wikipedia:Medical disclaimer doesn't say that we can't give medical advice? Because it doesn't. --Guy Macon (talk) 09:52, 29 September 2018 (UTC) Advising someone to obey the law does not constitute professional advice. ←Baseball Bugs What's up, Doc? carrots→ 12:31, 29 September 2018 (UTC) Actually, In my comment above I gave medical advice. To expand on my medical advice (which I remind you, I advise you to ignore because I am unqualified to give medical advice), don't become a meth addict even if the Libertarians win enough seats to control congress and legalize meth, heroin, etc. It will still be bad for your health. --Guy Macon (talk) 06:29, 30 September 2018 (UTC) Recommending not ingesting illegal drugs does not qualify as medical advice. ←Baseball Bugs What's up, Doc? carrots→ 09:44, 30 September 2018 (UTC) Also, since you've stated this same hypothesis a number of times, have you run it by the WMF to get the opinion of the owners of this website? ←Baseball Bugs What's up, Doc? carrots→ 12:46, 29 September 2018 (UTC) By my count, five individuals have asked WMF legal to issue a ruling that says that we are not allowed to give medical advice such as "don't do meth". WMF legal has declined to do that. Feel free to do your own asking. I am not going to ask because the WMF medical disclaimer (which, I remind you, does not say that we can't give medical advice) seems clear to me. --Guy Macon (talk) 06:29, 30 September 2018 (UTC) User Guy Macon pastes yet again his purported "allowed medical advice" in what looks like an opportunistic attempt to filibuster and provoke. The last time he did it [10] I pointed out[11] the error in his advice about crystal meth (which is Methamphetamine and is sometimes a legitimate medical prescription). Guy Macon defies suggestion that his rhetoric amounts to soapboxing[12] while he much more credibly admits ""When it comes to medical topics, an electronics engineer like myself is pretty much lost" [13]. I wish to distance myself from, and to reject as unacceptable and dangerous any medical advice like Guy Macon's that contains the phrase Don't bother asking a doctor.... DroneB (talk) 17:10, 29 September 2018 (UTC) ...Which, of course, you are free to do. In fact, I highly recommend ignoring (as opposed to rejecting; that would lead you to taking crystal meth) my medical advice, and doing your own research if you are considering taking crystal meth. I would even advise (which you should ignore) that if you are so dimwitted that you can't figure out that becoming a meth addict is bad for you without a M.D. telling you, then go ahead and waste your doctor's valuable time asking him whether to take crystal meth, and while you are at it, have him check your cognitive abilities, based upon your inability to figure it out without him. Please do ignore any medical advice I give you. Please do not make claims about imaginary "policies" that do not exist. Please do report me at WP:ANI if you honestly believe that my repeatedly correcting editors who fabricate imaginary policies and guidelines is disruptive. --Guy Macon (talk) 06:29, 30 September 2018 (UTC) Please see Wikipedia:Reference desk/Guidelines/Medical advice "Any question that solicits a diagnosis, a prognosis, or a suggested treatment, or any answer that provides them, is considered inappropriate for the reference desk." Dmcq (talk) 10:22, 29 September 2018 (UTC) Please show me where the Wikipedia community demonstrated a consensus for the above "policy". Until you do, per WP:LOCALCON (which is a WP:POLICY), the refdesk guidelines "have not formally been approved by the community through the policy and guideline proposal process, [and] thus have no more status than an essay". --Guy Macon (talk) 06:29, 30 September 2018 (UTC) (...sound of crickets...) --Guy Macon (talk) 02:36, 1 October 2018 (UTC) The disclaimer presumably gets the WMF off the hook legally. But does it get YOU off the hook legally? If you post medical advice, someone takes it, and something bad happens, might YOU be sued? That's the question to ask the WMF. ←Baseball Bugs What's up, Doc? carrots→ 09:41, 30 September 2018 (UTC) Go ahead and ask it. They will either ignore you or tell you that it is the WMF's job to insure that the WMF won't be sued, not to insure that I personally won't be sued. And it shouldn't be your concern either -- especially while you are in the process of evading any discussion about the established fact that you keep making up fake Wikipedia policies. I would really, really enjoy having someone try to sue me for telling people that crystal meth is bad for them. --Guy Macon (talk) 02:36, 1 October 2018 (UTC) That's not medical advice. ←Baseball Bugs What's up, Doc? carrots→ 03:50, 1 October 2018 (UTC)

Double streaming may be caused by a strand of hair across the orifice. This has no medical significance. Whether this is a problem for the circumcised but not the uncircumcised I am not in a position to say. 86.152.81.16 (talk) 12:03, 29 September 2018 (UTC)

It might be, or it might not be. Only a doctor can tell the OP. No one here is qualified to. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:29, 29 September 2018 (UTC)

I am with Bugs on this. Only a doctor can tell the OP. No one here is qualified to. All I can add is that it seems like the sort of thing one should see a doctor about. --Guy Macon (talk) 06:29, 30 September 2018 (UTC)

According to Pastry bag "Though a circular nozzle is quite useful for making round shapes and for filling pastries such as profiteroles, many differently shaped nozzles are commonly used to produce star, leaf, and flower-petal shapes." Bus stop (talk) 13:25, 29 September 2018 (UTC)

This is getting grosser by the minute. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:28, 29 September 2018 (UTC)

Might I suggest there are a couple of piss artists involved in the discussion. Dmcq (talk) 14:40, 29 September 2018 (UTC)

I don't know what that means, but it can't be good. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:47, 29 September 2018 (UTC)

See Wikt:piss artist. Alansplodge (talk) 17:22, 29 September 2018 (UTC)

Must be a British thing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:37, 29 September 2018 (UTC)

I would be tempted to use the term wanker, but as you might infer from my non-medical explanation above, I'm in no position to talk, as such usage would formally make them wankers' wankers, which is to say not wankers at all. The drolls are calling and they want the Internet back - the bureaucrats have tried and tried, but they don't know how to wring any real pleasure from it! Wnt (talk) 23:49, 29 September 2018 (UTC)

Speaking of wankers, some Yankees haters call this team "Wankees". In the AL Wild Card Game to be played on Wednesday between A's and Yankees, some A's fans would call the opponent team Wankees. If Yankees win and play the Red Sox in the ALDS, some Red Sox fans would call them Wankees.

Two of the good places to post medical questions are Quora and Yahoo! Answers, which already have a lot of them. PlanetStar 19:44, 30 September 2018 (UTC)

If it is supposedly "unethical" to answer medical questions here, then it is sure as shit unethical to send poor bastards off to be diagnosed at Yahoo! Answers. Wnt (talk) 01:37, 4 October 2018 (UTC)

I see someone is asserting there is no consensus support for WP:Reference desk/Guidelines/Medical advice. This is untrue. At WT:Medical_disclaimer#RFC_for_deprecation_of_this_policy overwhelming support for the policy and guideline were shown. People should not go around saying a policy or guideline is not supported without raising the matter there or on WP:VPP first and getting the matter resolved, deliberately misquoting policy is a serious business. Dmcq (talk) 11:03, 1 October 2018 (UTC)

So, is it your claim that a consensus for retaining a disclaimer THAT DOES NOT SAY THAT WE ARE NOT ALLOWED TO GIVE MEDICAL ADVICE is somehow relevant to a false claim that Wikipedia has a policy or guideline that says that we are not allowed to give medical advice?

The RfC you cite showed a strong consensus that the disclaimer does not say that we cannot give medical advice:

"I've brought this up, and asked this, multiple times: how is a disclaimer related to policy? I am willing to admit I'm wrong if I am grossly misunderstanding the term "disclaimer", or misreading it, but the Medical Disclaimer does not, in any sense, appear to be saying "You may not give medical advice", but "Do not construe what you read as medical advice, we don't intend it to be, it is not such in any legally meaningfully way and, thus, you are in error, and at your risk, should you so take it."

"Note the language of the disclaimer, it is not aimed at people editing, it is aimed at people reading and seems, pretty clearly, a legal protection rather than a policy."

"A disclaimer, by its nature is not a policy, thus, has no place in this discussion of policy - in other words: we are citing the equivalent of a "Do Not Try This at Home" warning, why? We actually have policies, and other such, it would make a lot more sense to refine those and deal with those, as opposed to discussing and citing something that is not such."

"I am not sure that there is a medical advice policy. I am fairly sure that this template is not the "medical advice policy", so I think that this RfC is misplaced. Even if there were a medical advice policy, and it were deprecated, then this template and page might still be useful. Maybe Jayron32 as the proposer can write a medical advice policy so that people can comment on retaining or deprecating it, or maybe Wikipedia is better without a medical advice policy."

"The Reference Desk guideline which says that respondents may not provide medical advice has very little to do with this disclaimer, which says that nothing you read on Wikipedia should be construed as medical advice. (It's unfortunately true that these two concepts, though distinct, are popularly conflated.)"

"The disclaimer is an instruction to readers, not writers."

"Time for a snow close: I think this request was mistaken. The responses are overwhelmingly in favor of the status quo. I see from the request that some reference desk editors wish to provide medical information in response to a borderline request for advice, but I don't see that as disputing the disclaimer itself."

"This Medical disclaimer is entirely appropriate and is independent of the nominator's concerns of how this policy should be applied to questions on the Reference Desks which might be interpreted as requests for medical advice."

"Even if the discussion that sparked this RFC represented some kind of consensus to abandon the longstanding Reference Desk guideline against providing medical advice (which I do not believe that it does), that would have nothing to do with the Medical Disclaimer, which should clearly stay in any case.

"The reference desk guideline and the Kainaw criteria look fine too, if a little restrictive, and the template looks harmless. They are not related to the disclaimer."

"I Object to this RfC on procedural grounds. Firstly, it asks about a "policy" when the real targets are an editing guideline that only applies to the Reference Desks, an essay in userspace, and a template that cites no policies. Secondly, it only allows two choices -- deprecating or maintaining Wikipedia:Medical disclaimer -- and does not ask to, say, turn Wikipedia:Reference desk/Guidelines/Medical advice into a supplemental essay such as WP:BRD, WP:CHILD, WP:CREEP, or WP:BPCOI. Another option that was not presented for a !vote is to create an actual policy (policy, not disclaimer) on this that applies to all of Wikipedia."

If you want Wikipedia to have a real policy that says what your imaginary policy says, post an RfC. Because that is not the consensus of the the RfC you just cited. --Guy Macon (talk) 17:02, 1 October 2018 (UTC)

If the intention is to warn the reader, then anyone giving medical advice should post the disclaimer along with their response, so there's less chance the user will take such advice seriously. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:42, 1 October 2018 (UTC)

That's an idea that I can get behind. It isn't currently required, but maybe it should be. Of course you or anyone else could respond with the disclaimer to a question asking for medical advice or to any answer to that question. --Guy Macon (talk) 21:02, 1 October 2018 (UTC)

As I recall, I had tried doing that for a while, but it seemed like it was not well-received. The user Medeis was a lot more aggressive about this issue. But that's history, as it appears Medeis is deceased. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:44, 1 October 2018 (UTC)

The RfC summary says "This is a strange request. Legally, Wikipedia may not give medical advice. Anybody using Wikipedia in order to do so is skating on extremely thin ice, unless their advice is always, and only, to consult a registered medical practitioner. In as much as there is a status quo here, it is the Wikimedia Foundation's responsibility to assess it and change it if necessary. There is certainly no consensus here for any change to existing practice."

This states what the closer believed the result of the RfC and the status quo to be. As far as I can see it is a fair summary. The RfC was raised on the Medical disclaimer and the reference desk guideline and. The guideline is marked as an edit guideline and has stood the test of time. If somebody wants to argues that the guideline is not a summary of the status quo and is not a proper guideline then they should raise their own RfC rather than asserting the invalidity of the guideline and trying to get others to do their work for them. Dmcq (talk) 22:27, 1 October 2018 (UTC)

The disclaimer does nothing to prohibit people from providing information on biomedical topics, and providing information on biomedical topics has nothing to do with the disclaimer or its prohibition on medical advice, an article linked in that RfC closure. Read the fuckin' article:

Medical advice is the provision of a formal professional opinion regarding what a specific individual should or should not do to restore or preserve health.[1] Typically, medical advice involves giving a diagnosis and/or prescribing a treatment for medical condition.[2] Medical advice can be distinguished from medical information, which is the relation of facts. Discussing facts and information is considered a fundamental free speech right and is not considered medical advice.

That's not my text, but it certainly backs my point of view. The RFC declined to change Wikipedia's disclaimer that it is not providing formal professional opinions regarding what a specific individual should or should not do to restore or preserve health. Which is a no brainer. Wnt (talk) 01:46, 4 October 2018 (UTC)

Indeed it is. Alas, I have seen a question about the best method for cleaning and disinfecting a shower deleted as "medical advice", and multiple deskref regulars defending the removal. --Guy Macon (talk) 09:38, 4 October 2018 (UTC)

The RfC also declined to do anything about the reference desk guideline and accepted it as common practice. If you wish to change that then raise an RfC with your desired change and see if it passes. On Wikipedia arguments against what is documented are worthless on their own. Dmcq (talk) 12:23, 4 October 2018 (UTC)

Or at the very least do a bold edit to the guideline making it say the opposite of what it says and so start a proper discussion at the right place instead of pushing your opinions here as if they counted for anything when you have shown no consensus. Dmcq (talk) 12:28, 4 October 2018 (UTC)

User:Kainaw/Kainaw's criterion is I think a reasonable criterion on whether to answer medical questions. If you follow that then disinfecting a shower should I believe be okay by pointing at standard advice about it. It does not need diagnosis, prognosis or treatment advice for a person. Dmcq (talk) 13:37, 4 October 2018 (UTC)

Why does ocean water get colder as you go deeper

When you go deeper in soil/rock, you reach higher temperatures because you approach a strong source of heat (Earth's core). But if you go deeper in ocean, temperatures decrease. Obviously I'd expect upwelling of warm water to carry off some heat from the bottom layers and lessen the temperature gradient, but how can they become even colder than the top layers? How does this not violate the second law of thermodynamics? 93.136.121.252 (talk) 23:30, 28 September 2018 (UTC)

There's a flaw in your logic. Whether you're on the dry surface or at the bottom of the ocean, you're on the Crust (geology). As suggested in Thermocline, the surface of the ocean is heated by sunlight and air temperature, and is fairly active. The farther down you go, the less active it is, so the warmer water does not mix in. Generally, the bottom of the ocean is calm and cold, because there is almost nothing to heat it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:44, 28 September 2018 (UTC)

The OP has a decent argument, but has neglected that ocean currents travel vast distances over long periods between different climates. See thermohaline circulation. It is true that the ocean is heated from below to some degree, but the water is gradually replaced with new water from the poles. I don't have any idea whether it would be theoretically possible to maintain a cold layer at the bottom of an ocean in a completely homogeneous climate by periodic (nightly) cooling with downwellings from the surface layer; I'm skeptical, but I think relevant data might exist from smaller seas and lakes in the tropics. Wnt (talk) 01:57, 29 September 2018 (UTC)

Yes, ocean currents make sense, I forgot that they might replenish cold water faster than the hot crust/mantle can transfer heat. Thermocline says that in polar waters temperature often doesn't decrease with depth. If there's sea ice then the surface should actually be colder (<4C), so that's probably where the cold at the bottom of warm seas comes from. Still, I'm pretty amazed that oceans can cool the Earth so much. In a shallow lake the day/night cycle can be significant, but when you look at deep oceans, even the 0-30C difference pales in comparison with the temperature differential at equivalent continental crust depth. 93.136.121.252 (talk) 04:07, 29 September 2018 (UTC)

I have heard that the pressure at those depths made the water reach its maximum density, which occurs at 4 degrees C. So the temperature at the bottom of a very deep lake is supposed to be that. I'm not convinced though, and I've wondered about it. 173.228.123.166 (talk) 04:28, 29 September 2018 (UTC)

Nope. Nothing about the pressure cools the water. And if the water was completely still, the heating from the core would be greater than it it is in deep mineshafts, because the crust is thinner at the bottom of the sea. Wnt got it right. The water isn't still, and whenever there is a difference in temperature (such as near the poles) the colder water sinks and then spreads out when it hits the bottom. https://oceanservice.noaa.gov/facts/coldocean.html explains it all. --Guy Macon (talk) 10:01, 29 September 2018 (UTC)

That's not the point. But water at 4°C is at its densest, so that's what sinks to the very bottom. In lakes, where there's no sideways ocean current, this becomes a stable layer. Andy Dingley (talk) 12:11, 29 September 2018 (UTC)

The Wikipedia article I cited earlier states that while the crust at the bottom of the sea is vertically thinner, it's also more dense. And the other article says the bottom of the sea is calm. I wouldn't take that to mean there's no circulation at all, but much less than there is higher up. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:42, 29 September 2018 (UTC)

Not really the point, but it is worth noting that the 4 C density maximum only applies to fresh water. For typical ocean salinity, the maximum density of sea water actually occurs at its freezing point (approximately -2 C). Dragons flight (talk) 18:38, 29 September 2018 (UTC)

I was puzzling over that, since I always understood that the zero point on the Fahrenheit scale was the freezing point of brine. However, the article indicates that the "salt" referred to is actually ammonium chloride. 86.131.233.235 (talk) 19:16, 29 September 2018 (UTC)

Water actually has one of the highest thermal capacities of all substances. Also water has the highest "volumetric heat capacity". That means it can store allot of (heat) energy but also takes or gives allot of energy when changing 1°. It also has a very good thermal conductivity for fluids. So it needs a constant high energy input to stay at or around some heat level.

That is the main secret behind the seemingly paradox about deep sea cold streams. The heat input from the earth core is barely enough to keep the water from freezing while the sun, nomatter it "heats" only half the time, manages to even warm up the top sea streams so much that they start to vaporize considerably. --Kharon (talk) 20:35, 29 September 2018 (UTC)

it needs a constant high energy input to stay at or around some heat level. Sorry, what? The most reading I can make of the above is that because water has high conductivity it transfers heat faster to close areas, thus gets to equilibrium quicker, thus needs higher incoming flux to match the outgoing flux. However, it is wrong on multiple levels. One: the relevant variable would be thermal diffusivity which is actually fairly low for water (about 100 times less than air, for instance), precisely because the thermal capacity is so high. Two: in most fluids of large dimensions, the dominant phenomenon of heat transfer is not diffusivity but convection; maybe that is different at the bottom of the sea because of anomalous density effects, but you cannot just blather about conductivity effects without discussing that first. Oh, also, "heat level" is not a thing. Try temperature or maybe internal energy.

The second paragraph's mumbo-jumbo seems to imply that the lower sea bed is kept liquid by heat from the Earth's core. Let's say I would like to see a source for that. Tigraan^{Click here to contact me} 09:56, 1 October 2018 (UTC)

Google "ocean heat level". Its a thing. Even a global one. Also i already mentioned the "temperature or maybe internal energy" you are missing, in my first sentence. Its "a thing" called Thermal capacity. Also water has no high thermal conductivity! Its 0.591 "k" (W·m⁻¹·K⁻¹) and only high compared with other fluids. Copper is 400 k. So copper is 236 times as thermal conductive as water!! Graphene is even 5300k.

You have to read more precise and complete instead of "generous", which you also failed. I added all these links to give readers a chance to understand the "mumbo-jumbo" terms. They are actually Thermodynamics terms btw. --Kharon (talk) 15:53, 2 October 2018 (UTC)

You confuse thermal conductivity and thermal diffusivity despite me wikilinking the latter in my reply. For the benefit of whoever actually reads my posts, k is the symbol for conductivity, not its unit (we do not abbreviate m/s by v, or s^{-1} by f). Tigraan^{Click here to contact me} 11:29, 3 October 2018 (UTC)

"k" is just a variable(formularsign). Its noted as common formula sign for Thermal conductivity in the first sentence of its article. I start to wonder if you lake the basics of Algebra or you just troll me, with superior tendency to the later. --Kharon (talk) 21:50, 3 October 2018 (UTC)

September 29

Are there any pathogens where the fraternal birth order effect makes a difference?

It's been established that the more older brothers a boy has, the more likely he is to be gay:

http://www.pnas.org/content/early/2017/12/05/1705895114

This fact, combined with Greg Cochran's theory about a pathogen being response for male homosexuality, makes me wonder:

Are there any pathogens where the fraternal birth order effect makes a difference? Specifically, are there any pathogens where the more older brothers a boy or man has, the more likely he is to be affected by this pathogen?

Basically, I am asking this question in order to get a rough idea of the likelihood of Greg Cochran's theory actually being correct. Also, No, I'm certainly not trolling; rather, I am trying as best as an amateur can in figuring out the truth behind this issue. Futurist110 (talk) 01:11, 29 September 2018 (UTC)

It doesn't sound like much of a "theory" where Cochran is concerned,

Can you please elaborate on this part? Futurist110 (talk) 01:30, 3 October 2018 (UTC)

but the association of homosexuality with a female anti-neuroligin 4 Y-linked (NLGN4Y) antibody is fascinating. This makes it sound like the antibody could be a simple case of an Rh factor like phenomenon; however, bear in mind that evolutionarily this "problem" could easily be "fixed" (women could express NLGN4Y anywhere in their bodies - big toe, salivary gland, wherever - and then it would end up being recognized as a self antigen and homosexuality would go away). This would indicate that far from being some insoluble design issue, homosexuality has been preserved by natural selection even in the face of a readily available mutation (putting some random enhancer on the DNA next to it). Which would mean that some very immediate selective benefit for homosexuality has to exist from the perspective of the mother.

Are you sure that a selective benefit has to have occurred? I mean, couldn't there be a gay germ instead which likewise evolves along with humans--thus ensuring that any immunity that humans will develop to this pathogen will become meaningless? Futurist110 (talk) 01:30, 3 October 2018 (UTC)

That said, Cochran's speculation isn't necessarily wrong -- anything is possible in biology, always. One can imagine that a foreign antigen could influence rejection of some other protein, like lone star tick causing meat allergy. The antigen could, in theory, be just about anything - mosquito saliva, rose thorns, or a virus. But the problem is, I am not aware of any demonstration that homosexuality has ever not existed in any human society, so how can it be an environmental factor?

I have heard either Cochran or someone else previously make the claim that homosexuality (or at least male homosexuality) doesn't appear to exist in hunter-gatherer populations. Futurist110 (talk) 01:30, 3 October 2018 (UTC)

It could be interesting to look into whether this particular neuroligin is responsible for the specificity of synapses between potential pheromone receptors (some orthologs are allegedly pseudogenes, but I'm suspicious of selenocysteine involvement) in the vomeronasal organ, and GnRH-expressing neurons that pass through the terminal nerve to the hypothalamus. If this antibody response can alter the determination of which odor is a pheromone, then it should be able to condition recognition of one sex rather than another. Wnt (talk) 01:50, 29 September 2018 (UTC)

Can this antibody response also alter the blueprint of one's body that one has in one's brain? Basically, I'm wondering if this antibody response could likewise cause gender dysphoria. Futurist110 (talk) 01:30, 3 October 2018 (UTC)

Here is a list of possible ways that natural selection can select for homosexuality as a trait that increases the success of an individual in reproducing and passing their genes on to the next generation: [ https://sites.psu.edu/evolutionofhumansexuality/2014/03/05/selection-for-homosexuality/ ]. --Guy Macon (talk) 04:38, 29 September 2018 (UTC)

Relevant articles: biology and sexual orientation and environment and sexual orientation. --47.146.63.87 (talk) 22:12, 29 September 2018 (UTC)

@Guy Macon: That article looks like a good review of at least most of the leading ideas. Problem? (a) Heterozygous advantage implies there is a "gay gene", which would have been mapped and cloned by now. People have tried hard and failed to map any one locus on the chromosome. (b) Altruism seems iffy in the article itself, as it is hard to explain how the homosexual can improve transmission of his genes that much in third parties; but see below. (c) A polygenic trait seems like a winner --- however, if women can simply express this neuroligin to prevent this antibody effect, then they can have a single gene trait that overrides it all, which is why I got excited to see the article. And (d) antagonistic pleiotropy only would make sense if the antibody response could also improve reproductive success (how?)

However, this paper introduces another possibility, which is that the mother could be selecting for her success, not the offspring's. It is always easier to tell somebody else to be altruistic than to be altruistic yourself, and so I think this might change some of the numbers, but I haven't looked into the math of altruism. Wnt (talk) 00:05, 30 September 2018 (UTC)

Diamond valuation

Is there someplace online where you can get a general idea of the value of a daimond (or even minor gemstones like, say, citrine)? I was reading about the 4Cs and am trying to figure out valuation by altering certain digits. Say how much would something like this cost? Color: I; Clarity: SI2; CTW: 0.200; Cut: RoundLihaas (talk) 09:41, 29 September 2018 (UTC)

This was the first hit on google for "diamond valuation", and puts your diamond's value at $147.42. 2400:D400:9:1268:306:200:0:10B0 (talk) 10:12, 29 September 2018 (UTC)

It's not clear from your post whether you're buying or selling. The price of a synthetic gemstone will generally be much lower than that of a "natural" one. Whether buying or selling, if you want a "natural" stone, you will likely get widely varying prices from different establishments; the market is intentionally opaque and full of collusion so you'll give up and just take whatever price is offered. (For instance, several of the largest U.S. jewelry store chains are owned by the same company.) --47.146.63.87 (talk) 22:07, 29 September 2018 (UTC)

This is a very old article but still relevant.[14] 173.228.123.166 (talk) 22:19, 29 September 2018 (UTC)

There is a company called the Jewelry Exchange in Redwood City, California that advertises "diamonds guaranteed to appraise for double". That ridiculous slogan indicates that diamond prices are mushy and subjective, as opposed to gold prices, for example. Cullen³²⁸ Let's discuss it 22:23, 29 September 2018 (UTC)

That's what I head, especially if they are lab made vs. natural.

Thanks, anywasy, yall.Lihaas (talk) 22:59, 29 September 2018 (UTC)

We have an article, though it's in bad shape. (No Cal resident? As the article says, their headquarters are down here, so here their ads always tout "The Jewelry Exchange in Tustin". I think they've been running the same TV ad for over 20 years.) --47.146.63.87 (talk) 08:11, 30 September 2018 (UTC)

September 30

Pianos vs motor vehicles: moving parts

A dear friend of mine, who's a highly experienced piano teacher, has told me that a piano has more moving parts than a motor car. I wonder if this would depend on the type of piano and the type of car. Or maybe it's absolutely correct. Or maybe not. Can someone shed light on this for me? -- Jack of Oz ^{[pleasantries]} 00:19, 30 September 2018 (UTC)

It could well be true. Start counting the moving parts in a typical car, and they might fall short of 88, or whatever the magic number would be. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:38, 30 September 2018 (UTC)

I can tell you it's way more than just the 88 keys. And I'm sure any car would have way more than 88 moving parts. -- Jack of Oz ^{[pleasantries]} 02:06, 30 September 2018 (UTC)

Have you asked your friend to "prove it"? Or might that be a sensitive issue? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:13, 30 September 2018 (UTC)

Do you count the cams on a cam shaft or the wheel weights on the wheel? Technically, every part on a car is a moving part if the car is moving, no??? ;) Wnt (talk) 01:59, 30 September 2018 (UTC)

A piano can also be moved via its wheels, but I'm not so sure the basic chassis of either a car or a piano would count as a "moving part". ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:13, 30 September 2018 (UTC)

These items claim that a piano has about 12,000 while a car has about 10,000. Piano and [15] ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:16, 30 September 2018 (UTC)

Our piano article cites a promotional website from Steinway & Sons, a piano building firm of international repute. The source claims: "There are 12,116 individual parts that make up a Steinway grand piano." This is not the same as 12,000 moving parts.

In any event, the number of parts - moving or otherwise - is a poor proxy for the mechanical complexity of a system. Not all moving parts are equal in complexity.

Personally, I find the non-moving part of the piano to exude more complexity: for example, the curved hardwood that forms the distinctive casing, or rim, of a grand piano commands a five-figure premium over the straight wall of an upright piano; and in both types of piano, the soundboard must be crafted in a manner that simultaneously satisfies strict engineering requirements and artful imprecision. As discussed in our article on piano acoustics, it is the inharmonicity of a piano - "not because of a lack of precision" - that give each instrument it timbre - and why it takes so much effort for electronic synthesizers to produce an authentic piano sound!

Nimur (talk) 03:24, 30 September 2018 (UTC)

Nobody mentioned complexity. Just numbers of moving parts. -- Jack of Oz ^{[pleasantries]} 03:43, 30 September 2018 (UTC)

{{ec}} with Nimur (had trouble tracking down the piano-article ref to verify) As a quick guesstimate, I count 15 moving parts in the action of a grand piano key, which gives 1320 total. That does not include the mechanism of shifting the set of hammers for the soft pedal, holding up all the dampers for the sustain pedal, etc. but those are likely^[SWAG] only a few tens each for the whole instrument or at most a few extra per key. DMacks (talk) 03:54, 30 September 2018 (UTC)

• Cars would generally be seen as having more, because the manufacturing processes used involve assembling together smaller parts. Consider a piano action vs. an engine cylinder. 88 keys, 11 parts in a piano action per key; 8 cylinders (or 4) - we can simplify this to "Does a car have more than 11 moving parts per cylinder?" Maybe 22 in Europe. Now the parts of that action are largely wooden, with many separate holes drilled into a piece of wood for each lever. The levers are few, but complex. But the car has separate parts, each staying separate until assembled by a mechanic in a garage (I'm counting parts which would be separated during repair as being "separate parts"). We have as many parts as a piano action just for each engine valve on an OHV engine. If you start counting balls in ball bearings, then it's far more. Andy Dingley (talk) 09:49, 30 September 2018 (UTC)

Small numbers of parts are replaced in routine car maintenance but a full restoration that considers all its parts happens only rarely, if ever, to a car or a piano. One cannot meaningfully compare counts of "moving parts" without an even-handed definition of what constitutes a moving part. Some extreme views are possible e.g.

• Every separable part that moves relative to another separable part when the piano/car is taken into use. The count includes screws holding the piano lid to its hinge, and every ball in the car wheel bearings.

• Literally every separable part because pianos and cars both have continual motions, both vibratory and planetary, relative to the fixed stars. The count includes every screw on both sides of the piano lid hinge and every chassis fastener in the car.

• A conceptual moving part counts as a single part regardless of its actual construction. For piano, key+hammer+string counts as 3, for car drivechain+camshaft+valve counts as 3.

A moderate view can be to count Every saleable replaceable part that moves in contact with another saleable replaceable part during normal continual use of the piano or car. For the car, the dealer's parts list is a guide. We may assume that a piston (with rings, gudgeon, connecting rod and big end shells) or a wheel bearing (preassembled with rollers and oil seals) count each as one. A piano key action should be separated into parts than a qualified repairer would consider replacing. This piano repairer estimates 12,000 action components. DroneB (talk) 19:59, 30 September 2018 (UTC)

Every component of every link in the timing chain would give you about a thousand moving parts. Your excellent attempt at stratifying the terminology is important, in this trivial problem.Greglocock (talk) 22:53, 30 September 2018 (UTC)

That's the 2nd example of intellectual snobbery on this thread. It says more about the writers of such things than anything else. -- Jack of Oz ^{[pleasantries]} 08:47, 1 October 2018 (UTC)

The Question is the famous comparing Apples and oranges nonsense. A Piano is meant to play 88 notes with a volume and dampening like the pianist intends, a engine is meant to provide a predefined jet flexible, efficient and secure transformation of fuel to rotation and Torque. The answer always causes the new question: "Yes/No, so what?" --Kharon (talk) 21:02, 1 October 2018 (UTC)

The OP raised the question because his friend made a statement about it. It seems like a reasonable question to ask. A more apples-and-apples question might compare a piano to a harpsichord. But the apples-and-oranges nature of the question is the point. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:20, 1 October 2018 (UTC)

Kharon, it depends on one's perspective. Yours is not useful here. Keep it simple. A piano is an object composed of many parts, some of which move when the object is in operation. A car is an object composed of many parts, some of which move when the object is in operation. How do the numbers of moving parts compare? -- Jack of Oz ^{[pleasantries]} 09:28, 2 October 2018 (UTC)

We may simplify the comparison to count the numbers of parts that move simultaneously. The wretched inadequacy of my piano playing ability is apparent when I encounter the 7 - gasp 7 -note chord in the 10th bar of Debussy's Clair de Lune. Although the piano is capable of playing all its 88 notes simultaneously under protest (from anyone within earshot), it will never Deo volente be asked to do so. The designer of the Yamaha PortaSound PSS-280 electronic keyboard seems in agreement because this instrument simply refuses to emit more than 7 piano notes at once. Can it be mere serendipity that an East German car was marketed with a 3-cylinder 2-stroke engine that has exactly 7 moving parts? Enough has been said and now like God we should rest on the 7th. DroneB (talk) 14:05, 2 October 2018 (UTC)

The seventh? DMacks (talk) 14:30, 2 October 2018 (UTC)

_{I fear the seventh both because 7 8 9, and to face an unlucky number 13 is risky. So I'll quietly take the fifth. DroneB (talk) 16:56, 2 October 2018 (UTC)}

Ok Jack of Oz. Let me help you on your perspective then. The Volkswagen Group 7993ccm W16 engine is a 16 cylinder 64 valve quad-turbocharged engine, that you can find in the Bugatti Veyrons and Bugatti Chirons and some Bentley models. It should beat any piano regarding number of moving parts since it already has almost as many valves (64) as a piano has keys. Given all the additional moving parts (for example in the fuel injection for 16 cylinders, oilpumps, fuelpumps, waterpumps, power generator, Starter (engine), Distributor, turbochargers etc.) a piano misses, lots of engines probably have more and a few very likely even more that double the moving parts. Btw. a 16 cylinder is not even the top of existing, build combustion engines in cylinder count. And your dear friend compared a piano to a whole car?

B.t.w. why are these pianos so damn expensive? Just cut a tree and you have enough material for the frame and mechanics for 5-10 pianos. How does Steinway get away with asking 81 000 $ for a single one? ---Kharon (talk) 14:37, 2 October 2018 (UTC)

Yeah, a Steinway is just a tree cut into pieces and re-arranged. --jpgordon^{𝄢𝄆 𝄐𝄇} 14:10, 3 October 2018 (UTC)

How does Barnes and Noble get away with asking $10 for a book? The price of paper and ink is not even a tenth of that. Tigraan^{Click here to contact me} 16:10, 3 October 2018 (UTC)

Berry

What berry is it? Grows this month along a public sidewalk in Warsaw, quite small, about the size of a blackcurrant. I'm planning to pick them for eating, if they're non-toxic, so would like to know the species with absolute certainty. Brandmeister^talk 15:51, 30 September 2018 (UTC)

Looks a bit like a cotoneaster - if so the berries are not considered edible. Mikenorton (talk) 20:49, 30 September 2018 (UTC)

I agree, looks very like a cotoneaster to me. DuncanHill (talk) 23:57, 30 September 2018 (UTC)

I disagree. The leaves in the picture are obtuse - not "ovate to lanceolate in shape". The fruits are borne singly or pairs close to the stem in the pictures - not on a corymb. I will try to track down a better candidate. 196.213.35.147 (talk) 13:37, 1 October 2018 (UTC)

Looks like it could be a cotoneaster after all. I'm going with Cotoneaster microphyllus var. glacialis 196.213.35.147 (talk) 14:01, 1 October 2018 (UTC)

"These berries are, however, of only doubtful or low toxicity" from Poisonous Plants in Britain and their effects on Animals and Man by the UK Ministry of Agriculture, Fisheries and Food.

Also "...as so often, the berries aren’t pleasant to eat. With the Cotoneaster, it is not so much that the taste is unpleasant, though it is, it is that the berries aren’t at all juicy and the texture is powdery. Even birds aren’t that anxious to eat the berries" ';'The Poison Garden Website. Alansplodge (talk) 14:47, 2 October 2018 (UTC)

Why do tinyish spiders often rappel when chased indoors?

Why don't they just jump off without expelling silk? They probably can't fall as fast as freefall while making silk and such a small creature might not even be injured by terminal velocity. Or did blowing away in the wind on a 1-thread parachute save more spider lives than "freefall and run" in its original outdoor habitat and the instinct remains? Sagittarian Milky Way (talk) 20:01, 30 September 2018 (UTC)

Our article ballooning (spider) may help. Mikenorton (talk) 20:57, 30 September 2018 (UTC)

You refer to "its original outdoor habitat". I very much doubt whether a spider, whether spiderling or adult, has either any concepts of "outdoors" and "indoors", or the perceptual abilities to tell the differences bearing in mind their size relative to a human-dimensioned structure. {The poster formerly known as 87.81.230.195} 90.217.102.65 (talk) 09:33, 1 October 2018 (UTC)

It goes without saying, as it is implied in OP's "and the instinct remains".

But even if spiders could distinguish indoors from outdoors (which should be possible, as there are so many differentiating factors they could evaluate: average wind speed, temperature, direction and intensity of infrared radiation and polarized light, smell), why should they just jump off without expelling silk? How could this be a selective advantage? Freefall speed is not the only relevant factor, another would be for example that the thread gives the spider a chance to withdraw from any less than optimal landing place, like water or perhaps the vicinity of predators and carnivorous plants or fire. 194.174.73.80 (talk) 13:31, 1 October 2018 (UTC) Marco Pagliero

If you really are asking how it could be a selective advantage, that's obvious: freefall speed could be the most important factor. I've no idea whether it is, but for what it's worth, the ballooning article doesn't seem to give any indication that the spiders can direct their flight. That would seem to imply that the other factors you mention are not significant. Henry^Flower 14:49, 1 October 2018 (UTC)

Please, you apparently did not read carefully the original question: it asks, why do small spiders "often rappel when chased indoors". Rappel has nothing to do with ballooning but instead describes a spider dropping e.g. from the ceiling on a line of silk. Even if the spider has no control on the direction, the thread allows it to stop and even to reverse the fall if it wishes so. In the context of rappel (not ballooning), my suggestions are of course significant.

And secondly you did not read carefully my own question, which read: "How could it be a selective advantage for a spider to just jump off without expelling silk?", this is the opposite of the question you seem to believe you are answering.

While for your post to be significant at all you should prove or at least make credible that such small animals as "tinyish spiders" can indeed be damaged when free falling from any height (We are not talking of Migale or Tarantula). 194.174.73.80 (talk) 16:35, 1 October 2018 (UTC) Marco Pagliero Berlin

"Migale"? Is there an article? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:40, 1 October 2018 (UTC)

Sorry, "Migale" is not English, you are looking for Mygalomorphae 194.174.73.80 (talk) 16:51, 1 October 2018 (UTC) Marco Pagliero Berlin

Marco, you've misunderstood completely. Not producing silk maximises freefall speed and so allows the fastest escape from the chaser. There's a fairly obvious selective advantage to that. (The ballooning issue is not so relevant, but you got that wrong too: SMW asked about "blowing away in the wind on a 1-thread parachute".) Henry^Flower 20:41, 1 October 2018 (UTC)

No, the question was "Why do tinyish spiders often rappel when chased indoors", while the parachute sentence you are citing was enbedded in a tentative response to this question but it doesn't imply the tinyish spiders SMW is chasing do actually try to balloon away (see the next sentence: 'can't fall as fast as freefall while making silk'). So I ask again, why should it be an advantage to spring without a thread beeing indoors if it is an advantage to spring with a thread beeing outdoors?

Your 'fairly obvious selective advantage' is not meaningful: whether you see the landing speed or the freefall speed as important, chased spiders never try to escape by ballooning but either by running or by rappeling, so your argument is pointless: ballooning is not a strategy for escaping when beeing chased and is not initiated by jumping without a fixed thread.

Well, even I can be wrong, so I'd like SMW to confirm whether he has ever seen a chased spider actually try to escape by 'blowing away in the wind on a 1-thread parachute' (Even our article on ballooning doesn't suggest anything like this) 194.174.73.80 (talk) 16:16, 4 October 2018 (UTC) Marco Pagliero Berlin

It doesn't have to be a selective advantage in all circumstances. It only has to be a selective advantage in a sufficient number of instances to provide a meaningful impetus to survival and reproduction. Bus stop (talk) 16:57, 1 October 2018 (UTC)

File:Amrum.grass.jpg

The dunes concerned.

Location known, but wanted to check something. The grass here gives way to a different cover, over what I am thinking is the landward portion of dunes?

Which articles should I look at to epxand the description? — Preceding unsigned comment added by ShakespeareFan00 (talk • contribs) 22:52, 30 September 2018 (UTC)

The green and purple stuff? Heather - so see Ericaceae, Erica, and Calluna vulgaris. DuncanHill (talk) 23:54, 30 September 2018 (UTC)

This paper should help narrow the options down. Mikenorton (talk) 16:57, 1 October 2018 (UTC)

This one may be more helpful (by the same botanist). Mikenorton (talk) 17:05, 1 October 2018 (UTC)

Thanks caption updated accordingly, if someone wants to review. ShakespeareFan00 (talk) 09:04, 2 October 2018 (UTC)

October 1

Toluene, water and isopropanol miscibility

I mixed one part toluene with one part 70% isopropanol and it separated into two phases. How do I determine what is in the lower phase? I'm guessing it's the water? — Preceding unsigned comment added by 185.230.100.66 (talk) 16:56, 1 October 2018 (UTC)

Density density density. More dense liquid sinks, less dense liquid floats. If you google fotr density of isopropanol water you will find various tables and specific values covering a wide range of percents. "70%" happens to be a standard product, and is directly available from simple product literature (i.e., no need to use scientific journals or paywalled sources), and probably even in the snapshot that Google provides on its list of hits. Of course our toluene article has the density of that pure substance. But once mixed, the more the IPA migrates into the toluene, the lower the %IPA in the aqueous phase and the denser the aqueous phase becomes. DMacks (talk) 17:59, 1 October 2018 (UTC)

Proportion of predicted progeny for a test cross of ABC/abc involving linkage

help i embarrassed myself as a tutor today. I don't have time to draw a diagram and a picture of the question would not be free content. Suppose there are three loci, A, B and C on a single chromosome, where A/B are 20 map units apart, and B/C are 10 map units apart:

• A — 20 — B — 10 — C •

Suppose we have a rat with the following genotype:

A B C
———
a b c

The question asks for the proportion of progeny with the genotype Aabbcc.

Whichever way I did it, I did not get 9%, which is what was shown on the answer key:

The only way to produce Aabbcc progeny is through Abc and abc gametes.

Assuming no double crossovers between same loci (but allowing for double crossovers between different loci): the gamete frequency for abc is 0.9 * 0.8 * 0.5 = 36% (chance of no crossover betwen either pairs of loci * half the gametes) and for Abc is 0.2 * 0.9 * 0.5 = 9% (chance of crossover between A/B * chance of no crossover between B/C * half the gametes) so the expected frequency should be 3.24%.

How is the answer key (9%) correct? Yanping Nora Soong (talk) 18:11, 1 October 2018 (UTC)

• Disclaimer: I just discovered the topic of crossovers (but not probabilities).

There is an error in your reasoning when you assumed the first gamete must be abc and the second Abc (it can be the other way around) so you miss a factor of two. (Out of the 36 outcomes when you cast two dice, only one is a double 1, but two contain one 1 and one 2 - if that is not obvious to you, or for further reading, see [16].)

Furthermore, the probability of crossover is not strictly proportional to the distance so it is not exactly 80% and 90% chances of no crossover. The formula at Centimorgan#Relation_to_the_probability_of_recombination should be valid only if double crossovers are allowed (since at infinite distance the probability of recombination tends to 1/2, which comes from the fact that an odd or even number of crossovers is equally likely), but yours (P = d/100) is pretty much never right I think (except for small-d approximations). Using the article formula I get crossover properties of P10=9.06% and P20=16.48% (instead of 10% and 20%).

Your reasoning for gamete frequencies seems correct to me and gives $P(abc)=(1-P_{20})*(1-P_{10})*0.5=37.97\%,P(Abc)=P_{20}*(1-P_{10})*0.5=7.49\%$. The final probability of genotype is then $P(Abc+abc)=2*P(Abc)*P(abc)=5.69\%$. While it brings one closer to the result, that is still not the answer key. Tigraan^{Click here to contact me} 14:21, 2 October 2018 (UTC)

It's been a while since I've dealt with something like this but since we are talking about rats, which don't naturally self fertilise, have I misunderstood something or is there no way to give a single progeny diploid genotype frequency based on the question as worded? There is only one rat mentioned. We have no idea what the genotype of the other parent is. It could be anything e.g. abc|abc, ABC|ABC, a'b'c'|A'B'C'. You could only give a range from 0% (if the other parent has none of those alleles) to the maximum possible (assuming the most favourable parent to produce that combination when mating with the parent who's genotype is mentioned). Are you sure that the question didn't say something like 'assume both parents are ABC|abc' or 'if the rat self fertilises' (which is a very odd suggestion but I'm sure far from the weirdest test question) or something which would clarify the situation? Nil Einne (talk) 19:26, 2 October 2018 (UTC)

Your original calculation came up with a 9% figure for Abc. So the way to get the book's answer is to suppose they threw in the word "backcross" somewhere, or a comment about the phenotype of the other parent being abc, etc. The assumption of no double crossovers between adjacent genes is reasonable, though the statement that they are 20 and 10 centimorgans apart (rather than having this observed probability of recombination) would make it an approximation. Wnt (talk) 01:45, 3 October 2018 (UTC)

I asked my genetics professor from eight years ago, and she made me realize I confused a test cross with a self-cross. Oops. Yanping Nora Soong (talk) 16:31, 3 October 2018 (UTC)

Remember that providing key question details in the subject heading only on the RD is quite confusing since it's fairly common that people will only skim over or even just not notice the heading. Nil Einne (talk) 19:33, 3 October 2018 (UTC)

Indeed so! Also, people tend not to Wikilink from headers since it is "frowned upon", whereas if the OP had linked test cross in the question, he or she might well have gotten to his own answer in the process. Wnt (talk) 01:51, 4 October 2018 (UTC)

I wrote this question from my phone, which is quite different in "feel" than writing from my laptop. Yanping Nora Soong (talk) 15:46, 4 October 2018 (UTC)

October 2

Why did it take so long to invent the heavy plough?

The heavy plough is hailed as one of the most revolutionary technological advances in the history of agriculture. But, from what I've read, the heavy plough is, quite literally, just a heavier version of the regular plough. Why did it take so long to invent, then? — Preceding unsigned comment added by 90.69.6.163 (talk) 10:05, 2 October 2018 (UTC)

The Plough invention described was replacement of the simple ard by the carruca turnplough around the 7th century, though a heavy iron moldboard plow was already developed in China's Han Empire in the 1st and 2nd century. The carruca may have been introduced to the British Isles by the Viking invasions of England in the late 9th century. The article Iron Age gives estimated dates for the spread of iron tool- and weapon-making around the World but cannot explain "Why not earlier?". DroneB (talk) 13:09, 2 October 2018 (UTC)

See https://www.deere.com/en/our-company/history/john-deere-plow/. The main rise of technology came with the rise of industrialization and mass transport. Maybe someone already invented it in the roman empire but no one cared because it was slave work anyway and much cheaper to buy additional slaves to do double the work. --Kharon (talk) 15:01, 2 October 2018 (UTC)

• What relevance does John Deere (who were one of the inventors of the steel plough) have, a thousand years after the invention discussed here? Andy Dingley (talk) 22:38, 2 October 2018 (UTC)

"The scratch plow which preceded the wheeled plough had been ideal for the light sandy soils of Southern Europe" which means that the heavy plow was probably not necessary in Italy. Ruslik_Zero 12:28, 3 October 2018 (UTC)

• It isn't merely heavier. It's also wheeled and (most importantly) uses a more robustly constructed share and mouldboard, capable of turning a furrow, not merely acting as a harrow. Which also requires a greater investment of iron, still a highly valuable material in this period. Additionally it also requires a team of draft oxen to pull it (oxen rather than horses at that time). You can't pull it with a donkey, or a couple of friends. Andy Dingley (talk) 22:38, 2 October 2018 (UTC)

Can anyone identify this caterpillar (Vietnam)

Hi

I was wondering if anyone could identify this caterpillar? A colleague/friend is on a work trip to Vietnam and took this photo.

Hermitical (talk) 23:10, 2 October 2018 (UTC)

October 3

What are the odds of conceiving the exact same embryo in these two scenarios?

Here are the two scenarios:

In the first scenario, you conceive an embryo through intercourse. Meanwhile, in the second scenario, you conceive an embryo through in vitro fertilization (IVF). Let's say that the second scenario happens in a parallel universe at the exact same time that the first scenario occurs in this universe.

Anyway, what are the odds that the two embryos conceived in these two parallel universes would be the exact same embryo? Futurist110 (talk) 01:59, 3 October 2018 (UTC)

Depends on who is the father of the child. 86.152.81.16 (talk) 10:21, 3 October 2018 (UTC)

175983257964128056 to 1. — Preceding unsigned comment added by 82.38.221.49 (talk) 12:23, 3 October 2018 (UTC)

An interesting question, but I don't know how you'd get to the answer. I assume from your premise that the gametes in each universe would be identical (otherwise you are asking the usual question of what would have happened if another sperm had won the race). But is there any detectable effect of the procedure? Well, the in vitro fertilization article has two sections about suspected issues ranging from birth defects to hypertension. Whether these are accompanied by any subtler, non-medical change to the offspring is another question. Wnt (talk) 12:40, 3 October 2018 (UTC)

• If you are asking about embryo development differences between IVF and the ol' way, ask it, instead of masking the question in a layer of probability. (I cannot answer that.)

If the real question is about the probabilities that offspring of the same parents has the exact same genetic code... That is the Shannon entropy of offspring DNA. There's a good argument for why DNA entropy is not well-defined but I guess you could easily produce something that looks like a definition; for instance, "for every gene with multiple alleles, estimate the prevalence of each allele, and compute the entropy by assuming genes to be independent (which they obviously are not in reality)". Tigraan^{Click here to contact me} 16:26, 3 October 2018 (UTC)

100% odds, as there is always going to exist a sector within that parallel universe where the required conditions for the exact copy to arise will be met. Count Iblis (talk) 17:34, 3 October 2018 (UTC)

Inheritance of hair color

I'm interested in under exactly what circumstances a child inherits a specific hair color from its parents. In general, how well understood is the genetics of this? A more specific question is, what hair color would a child of a red-haired father and a blond-haired mother inherit? FreeKnowledgeCreator (talk) 02:33, 3 October 2018 (UTC)

You might find Human hair color helpful. It appears that there are other factors than the visible hair colour that have to be taken into account when attempting such predictions. Richard Avery (talk) 08:51, 3 October 2018 (UTC)

Thank you. It's disappointing to see, however, that the article's section on "Genetics and biochemistry of hair color" is uncited. I'm presuming my more specific question doesn't have a clear-cut answer? FreeKnowledgeCreator (talk) 09:28, 3 October 2018 (UTC)

"There is very little known about hair color inheritance but there are some interesting theories" from The Stanford Department of Genetics.

A better referenced article is Red hair color: The myth from John H. McDonald, University of Delaware. Alansplodge (talk) 12:25, 3 October 2018 (UTC)

A newspaper article from April this year: Scientists discover dozens of new genes for hair colour

The research the article describes seems to be Genome-wide association meta-analysis of individuals of European ancestry identifies new loci explaining a substantial fraction of hair color variation and heritability. Alansplodge (talk) 12:33, 3 October 2018 (UTC)

Does the MRI produce radiation?

I've been under the impression that MRI is dangerous because of a potential radiation exposure. However yesterday I talked to a radiation technician and she said: "No, MRI is all magnetic." I could have found out myself, I want a verification, but it will take longer, so please advise. Thanks. AboutFace 22 (talk) 13:19, 3 October 2018 (UTC)

Have you read our article on MRI? Plenty of verification there. --Shantavira|^{feed me} 13:25, 3 October 2018 (UTC)

If you have concerns about safety, you should ask to speak to the radiologist (who is a medical doctor), not just to the technician who operates the machines.

To clear up the basic physics: an MRI works by emitting and detecting radio-frequency radiation while exposing the test-subject to a powerful static magnetic field. An MRI does emit radiation.

Not all radiation is medically harmful. Review the definition of radiation - the transmission of energy - which takes many forms, including electromagnetic waves of all different types. Consider that ordinary light-bulbs emit large amounts of electromagnetic radiation in the visible light spectrum. Medical harm is caused when the radiation is especially strong, or if it has other special physical properties - like the ability to ionize or otherwise disrupt a material.

Certain categories of radiation are particularly noteworthy for their adverse medical effects on humans: among them are ionizing radiation and the radiation of particles from certain nuclear processes. Broadly speaking, an MRI does not emit ionizing radiation. An MRI does radiate energy in the form of a powerful electromagnetic wave, but it is at a frequency that is generally considered safe for human exposure.

MRIs are classified, by the FDA, as a radiation emitting product. This is accurate from a physical point of view.

Properly-maintained machines are safe and legal for medical use in the United States, subject to many special considerations. In addition to the machine itself, a patient in a normal clinical setting might also be exposed to radiation from other sources at the clinic, including other lab equipment and radiological materials used for diagnostic processes.

One last note: technicians in the clinic are not necessarily experts on the theory of the machine - they are trained in operating it. So, they might not be the best resource for explaining how the machine works.

Nimur (talk) 13:42, 3 October 2018 (UTC)

Or even better, talk to a health physicist (a physicist, not a physician) who understands specifically the medical physics of what the various machines do produce and whether it's a problem. Nor would I undervalue the knowledge of a good operator.

MRI machines do have hazards (magnetism, cryogenics, induced currents), but they're well understood and don't have long-term risks. But (simply put) if you make it in and out of the machine without an obvious accident, you're not going to develop unwanted Superpowers down the line. Andy Dingley (talk) 13:59, 3 October 2018 (UTC)

We have a well referenced and reassuring article Safety of magnetic resonance imaging but there is also in-hospital gossip and sensational reports such as "Man dies after being sucked into MRI scanner at Indian hospital" that serve to maintain awareness of the overriding danger of an MRI scanner which is not radiation but its strong magnetic field that can snatch up a steel Wheelchair with its patient. DroneB (talk) 16:23, 3 October 2018 (UTC)

To the average person, "radiation" means ionizing radiation. Or, more accurately, "scary evil invisible manmade stuff that can KILL YOU AT ANY TIME! RUN AWAY!" --47.146.63.87 (talk) 07:12, 4 October 2018 (UTC)

I appreciate the explanations, so the technician was correct. I work at a place where there is an MRI machine, or at least it is my impression, but there are no radiological MD. They transmit images electronically to a large medical center. They simply do not have enough volume. I will find out if they have an MRI machine though. Thanks very much to Nimur, Dingly, DroneB. AboutFace 22 (talk) 16:54, 3 October 2018 (UTC)

They tell you not to bring objects attractable by magnets and electronics that are keeping people alive like pacemakers into the area right? Those are a lot more important than the radiation. Once there was an accident where some idiot turned on the MRI while a steel gas tank (O2? or would that rust like hell or spontaneously explode?) was in the room and it flew towards the magnet and hit the machine at high speed. Sagittarian Milky Way (talk) 18:12, 3 October 2018 (UTC)

You don't "turn on" an MRI machine's magnet. The main magnetic field is either a superconducting magnet, or else (rarely) a permanent magnet using rare earth magnets. Neither of these are switchable. This is why MRI machines are kept in their own rooms (or rooms beyond rooms) and there's a "quarantine" system so that magnetic objects aren't taken beyond the door. When they are, accidents happen. Andy Dingley (talk) 20:49, 3 October 2018 (UTC)

To be pedantic, you don't in normal operation. If things go pear-shaped a magnet quench occurs, which is very expensive. And obviously the machine is shut off in a more orderly fashion for service, to be moved, or whatever. Also for educational purposes: the above poster is discussing how the MRI room is enclosed in a Faraday cage, to contain the field of the magnet as well as keep out interference. --47.146.63.87 (talk) 07:12, 4 October 2018 (UTC)

bug ID

https://postimg.cc/RJnzmp7v

North/Central Europe. Is it parasitoid? Thank you everyone Asmrulz (talk) 13:47, 3 October 2018 (UTC)

Looks like a woodlouse to me. Rojomoke (talk) 15:44, 3 October 2018 (UTC)

Oniscus asellus? Mikenorton (talk) 16:24, 3 October 2018 (UTC)

How far from Earth before the densest air stops being equatorial?

I imagine it might vary somewhat with things like solar activity, time of day and atmospheric tides (perihelionic New Moon perigean spring tides are the strongest and about as far from the atmosphere's equatorial bulge as can be, sometimes both Sun and Moon are equatorial at the same time leaving only the miniscule tides of things like Venus) Sagittarian Milky Way (talk) 18:01, 3 October 2018 (UTC)

Earth atmosphere is not an equally round sphere but more like a drop with a tail in the direction opposite to its orbit vector around the sun, Just like a comet tail but much shorter, because the earth gravitation is way stronger than a comets one. Never the less the "tail" of the Earth actually also causes some Atmospheric escape. Because the Earth axis is slightly tilted and the atmosphere "drop" is shaped mostly by gravity and solar winds, the shape of the atmosphere is not "equatorial" at all. --Kharon (talk) 22:29, 3 October 2018 (UTC)

Maybe Wikipedia could get an article on Equatorial air mass, so users like Kharon would have the opportunity of understanding questions like the one above and spare us all of some nonsense answer. Apart from that, the Air mass article has links in the right direction. Doroletho (talk) 22:47, 3 October 2018 (UTC)

vision is by far the most used of the five senses?

I just read a phrase in an ophthalmology book and I'm absolutely not sure about it: "vision is by far the most used of the five senses". Is it really correct? I would say that the hearing or smelling is the most used since they are open involuntarily unlike the eye that at night close as well as many times a day when blinking the eyelids. Isn't it? — Preceding unsigned comment added by 93.126.116.89 (talk) 18:40, 3 October 2018 (UTC)

It is the most used in sense that humans receive more than 90% of information from vision. Ruslik_Zero 20:52, 3 October 2018 (UTC)

Vision records the largest volume of data in humans. In that sense its most used but its not active when we sleep and you wont wake up from light but certainly from sound. So sound is used around the clock without brake. "Most used" is an incomplete quantification because its missing in what regard. Time? Data volume? Sensitivity? --Kharon (talk) 22:44, 3 October 2018 (UTC)

What's the relation between fire and electricity?

I'm looking for differences between fire that comes from an electricity (for example electrical stove) and fire that comes from a real fire. If your religion would tell you that you aren't allowed to use fire for cooking did you used electricity or did you not use it. Kindly let's put aside our opinion about religion at all and try to answer scientifically about the question and give a reason why to resemble or not resemble between the two. I've red a lot of articles on wikipedia and I'm really confused and I believe that great part of it is because I don't have enough (deep) background or 'infrastracture' in sciences. Then please try to explain me in simple words as simple as possible and I'll appreciate it a lot. 93.126.116.89 (talk) 18:52, 3 October 2018 (UTC)

Fire is a rapid chemical reaction in which other elements combine with oxygen to form new molecules consisting of the other elements and the newly-added oxygen. Electricity (in the sense used to create heat) is the passage of electricity through an element that resists, but does not totally block, the passage of electricity. No chemical reactions occur in the electric heating appliance (although chemical reactions may be occurring at the power station where the electricity is being generated). A practical difference is that the gases created during fire are not entirely safe. While a small fire, such as a modern gas kitchen stove, can be used in a room with no planned, active ventilation, a larger fire, such as that needed to heat a house, must be vented to the outdoors with a chimney or equivalent measures. Jc3s5h (talk) 19:01, 3 October 2018 (UTC)

Thank you for your answer. Just to clarify that I understood you answer let me ask something please. you said "No chemical reactions occur in the electric heating appliance". But if I'm not mistaken, physically or microscopically, the eating occurs by the action of electrons moving in the metal very fast and that's what causes heating. isn't it? or maybe I didn't understand your words? 93.126.116.89 (talk) 19:44, 3 October 2018 (UTC)

Electric cookers (with some modern exceptions, such as the microwave oven and the induction hob) work by resistive Joule heating. Electric current in a metal wire flows because the electrons are no longer attached to each atom of the metal but can move quite freely within the metal, between the atoms. They collide with the atoms though, which loses their energy as vibrations, which we then detect outside as heat.

This is not fire though. Fire is a chemical reaction, usually an oxidation and the combination of some fuel with the oxygen in the air as the oxidiser. Each reaction releases a certain amount of energy (this depends on the chemistry involved) and this energy is seen as heat.

Although the end result of both is heat, the mechanisms to produce it are unrelated. Andy Dingley (talk) 20:44, 3 October 2018 (UTC)

A simple Chemical reaction is when two substances combine to produce new substance(s). What we call Fire is commonly the Flame that we see when such a reaction happens to be strongly exothermic (releases heat energy). Familiar examples are whenever a Fuel is consumed by burning in air. Use the links in bold to read more detailed articles. Chemists describe the reactions in burning by equations such as the example below. It describes the burning of hydrogen gas whose end product is simply water; this is a chemist's explanation of the conflagration in the Hindenburg disaster.

2H
₂ + O
₂ → 2H₂O

Be careful with the expression electric fire which in British English means a heating appliance that is powered by electricity. There should be no chemical reaction of fire in such an appliance (room heater, cooker, hairdryer, clothes iron, toaster, etc.) They have internal resistive heating wires made of some metal alloy e.g. Nichrome and this alloy material does not change during the lifetime of the appliance.

Examples of relations between fire and electricity are 1. Electricity in the form of a spark can trigger the start of a fire, as when lightning starts a forest fire, provided there is fuel available for the fire. 2. Fire can be used to heat water to drive a steam generator, thus converting the energy in a fuel to electric power. DroneB (talk) 21:57, 3 October 2018 (UTC)

Chemical reactions can also change a reactant into a simpler substance. Digestion furnishes lots of such examples. As the article says, a chemical reaction involves a transformation of one or more chemicals into other chemicals. There is something of a similarity, at the level of physics, between redox reactions and electric current, since both involve a flow of electrons or other charge carriers, though this doesn't mean they're the exact same thing. Living systems demonstrate this link quite well: your cells produce electric charge gradients by using enzymes to pump ions around, all fueled by the release of chemical energy stored in the food you consume. --47.146.63.87 (talk) 07:26, 4 October 2018 (UTC)

The religious issue you raise can get quite thorny. See Electricity on Shabbat for the example of Orthodox Judaism. --47.146.63.87 (talk) 07:26, 4 October 2018 (UTC)

US Patent no. 7872576 introduces a notion that a manually operated switch whose effect is by design incompletely predictable can somehow reduce the personal responsibility of operating an electric light (said to be a no-no for some Jews on the Sabbath or holy days) or of actions such as discontinuation of life support for terminally ill patients, triggering of a lethal dose in a death sentence, or discharging of a weapon. The article KosherSwitch does not show how this alleged Sabbath-compliant (Shomer Shabbat) device works or address the question of what degree of pseudorandomity is close enough to unpredictable randomity (in the sense of Schrödinger's cat experiment) to impress the God of Abraham as Exculpatory evidence. DroneB (talk) 10:57, 4 October 2018 (UTC)

• Feel free to ask away question about the physics if the above is insufficient. When it comes to the religious law part, I think the correct answer here is the same as for actual law: consult with whoever you feel has actually the authority to make judgement of whether a given course of action is or is not compatible with your religion, rather than asking a bunch of random internet folks. As evidenced by Activities_prohibited_on_Shabbat#Igniting_a_fire, a statement that is scientifically correct ("there is no fire in incandescent light bulbs" is pretty much uncontroversial when "fire" is meant to mean flame) does not necessarily translate into religious rule (at least according to some Orthodox Jew authorities, light bulbs violate the no-fire rule, but of course "fire" in a religious sense might be more than a bunch of chemical reactions). Tigraan^{Click here to contact me} 15:33, 4 October 2018 (UTC)

File:Leech crawling.webm

File:Leech crawling.webm is described as a leech, but it looks more like a Bipalium planarian in light of its head. Anyone know what it actually is? Jo-Jo Eumerus (talk, contributions) 19:24, 3 October 2018 (UTC)

Yes, it resembles a Bipalium flatworm. Ruslik_Zero 20:50, 3 October 2018 (UTC)