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January 20

Weather machine

Did anyone ever actually attempt to create a device for the purposes of manipulating the weather? Once read something about how the US military looked into how the butterfly effect could be weaponized to cause weather in Russia that would lead to droughts, floods, tornadoes, etc. - some facilty in Alaska? Also that the Russians were trying to do it too, but that it didn't work and so everyone gave up on it. Probably a conspiracy theory (I enjoy reading those sometimes), but just curious. 146.200.129.104 (talk) 11:55, 20 January 2022 (UTC)

See weather modification to see various efforts to manipulate the weather, to varying levels of success. Wikipedia has an article on everything. --Jayron32 13:18, 20 January 2022 (UTC)

For a conspiracy theory, see HAARP#Conspiracy theories. 2603:6081:1C00:1187:25B6:3B5:BCF7:4392 (talk) 14:55, 20 January 2022 (UTC)

The butterfly effect is that a butterfly wing flap on the other side of the world could literally be the difference between a hurricane or no hurricane years from now, there's no possible way humans could predict that. How do you have a years-long 24/7 video of the movements of a cow who isn't even born yet? Much less the entire world, even in caves? Sagittarian Milky Way (talk) 16:36, 20 January 2022 (UTC)

Except that the so called "butterfly effect" is not literally that a butterfly flaps its wing and it could mean the difference between a hurricane or no hurricane years from know. It is an analogy to explain how small changes in initial conditions can have large effects on outcomes of models. As stated in our article: "Of course the existence of an unknown butterfly flapping its wings has no direct bearing on weather forecasts, since it will take far too long for such a small perturbation to grow to a significant size, and we have many more immediate uncertainties to worry about. So the direct impact of this phenomenon on weather prediction is often somewhat wrong." A large initial perturbation CAN have a measurable impact, and one that is far easier to predict than a small perturbation.. --OuroborosCobra (talk) 18:35, 20 January 2022 (UTC)

The fact that I said you'd have to account for the cows and the caves and everything else in the world 24/7 shows that I knew the butterfly was just an example. Is a large initial disturbance (like nuking a hurricane I guess or maybe cloud seeding) really what scientists mean when they say the butterfly effect? I never said such tiny air disturbances could be accounted for in weather forecasts, in fact I said it could never be. No one could possibly make a model of the atmosphere that accurate. And since the minimum air disturbance size that materially affects the weighted random number generator that is weather shrinks with longer time horizons there definitely should be a time that's far enough in the future that every tiny animal movement now will change all the weather after then (without materially changing the climate probabilities, i.e. a dinosaur or Cro-Magnon couldn't have materially changed the percent of the 2nd millennium at 52°N 0°E 1km above sea level that was rain). Sagittarian Milky Way (talk) 19:24, 20 January 2022 (UTC)

Power source for Jupiter's aurorae

Does their energy ultimately come from Jupiter's rotational energy or from its internal heat (via convective dynamos)? I've been looking for papers but none explicitly analyzes these questions. JoJo Eumerus mobile (main talk) 20:44, 20 January 2022 (UTC)

The mechanism for the Jovian aurorae is basically the same as for the terrestrial aurorae: ionization and excitation of atmospheric gases by charged particles affected by disturbances with the planet's magnetosphere. The source of these particles on Earth is primarily the solar wind; from the JADE results it is known that there is an important other source in play on Jupiter. The magnetic field forming the magnetosphere is thought to be generated by what is called an "interior dynamo", but the mechanism is poorly understood. Here are links to scholarly articles on dynamo models for Jupiter.  --Lambiam 21:18, 20 January 2022 (UTC)

Agreed: These dancing lights are produced when energetic particles from the sun or other celestial bodies slam into a planet's magnetosphere — the area controlled by a world's magnetic field — and flow down its magnetic field lines to collide with molecules in its atmosphere. Jupiter's magnetic field is extremely strong — about 20,000 times more powerful than Earth's — and therefore its magnetosphere is extremely large. If that alien magnetosphere were visible in the night sky, it would cover a region several times the size of our moon. As such, Jupiter's auroras are much more powerful than Earth's, releasing hundreds of gigawatts — enough to briefly power all of human civilization. [1] Alansplodge (talk) 21:29, 20 January 2022 (UTC)

Their energy mainly comes from the Jupiter's rotation. See magnetosphere of Jupiter. Ruslik_Zero 20:23, 21 January 2022 (UTC)

Thanks. JoJo Eumerus mobile (main talk) 20:52, 21 January 2022 (UTC)

Can there be an immediate way to broadcast sound in the universe? "Bypassing relativity"?

I understand that the stars we see are actually light from stars that existed in the past (billions/trillions of years ago) and may no longer exist today, so the light is still "doing it's way" to us (even though it travels in a blazing speed).

Is there really no way to broadcast signals (light/sound) without this "slowness"? For example, is there no way for humans, at least in theory, to broadcast sound signals to other galaxies in some **immediate media**, bypassing the common situation of fast-but-slow *light speed travel*? — Preceding unsigned comment added by 79.176.222.75 (talk) 23:04, 20 January 2022 (UTC)

Maybe via tachyons, if they exist? (Otherwise, you'd have to get some unobtainium to build a transmitter, although it is rumored that gossip travels much faster than the speed of light.) Clarityfiend (talk) 23:37, 20 January 2022 (UTC)

Quoting our article Faster-than-light, oddly named, but whose topic is, specifically, faster-than-light communication:

Particles whose speed exceeds that of light (tachyons) have been hypothesized, but their existence would violate causality, and the consensus of physicists is that they do not exist, and their existence would imply time travel.

Actually, the mere assumption of the possibility of faster-than-light communication in a universe satisfying basic special relativity, regardless of the communication medium (waves, particles, telepathy, morphogenetic fields, Infinite Improbability Drive), already clashes with causality. If event S (send info) precedes event R (receive info) in some observer's frame of reference, and their separation implies FLT communication, the interval between the two events is spacelike in the Minkowski metric. This implies there is another frame of reference in which, for its observers, R precedes S: the message is received before it was sent.  --Lambiam 01:00, 21 January 2022 (UTC)

That by itself is not necessarily a problem; that time is just a coordinate value you assign to the event, and it's OK in and of itself if the number is smaller. What's really a problem is if you can get a causal loop, which you can, if the faster-than-light communication conforms with relativity. We have an article: tachyonic antitelephone.

Note that there is an assumption here. What if relativity doesn't work for tachyons? Maybe there is a preferred frame of reference, but you can't tell if you just look at photons and bradyons, which is all we've ever observed. This would fit with a neo-Lorentzian interpretation of special relativity, generally disfavored in the current day, but on metaphysical rather than empirical grounds. --Trovatore (talk) 01:20, 21 January 2022 (UTC)

This reminds me of TV ads where (unlike real life) the Twin Towers roof had a microphone and giant speakers and the bald guy would say "the New York Lottery jackpot is now (number).. MILLION.. DOLLARS!" and people are shown confused by the booming sky voice's existence at ever increasing distances and very exaggerated volume dropoff slowness finally ending with it still being loud enough to understand over the roar of Niagara Falls (hundreds of miles away). I always wondered if each TV market got a local version. Sagittarian Milky Way (talk) 01:13, 21 January 2022 (UTC)

Monarchy --Verbarson ^talk_edits 16:21, 22 January 2022 (UTC)

Abdication emits an intense burst of kingon radiation that irradiates the entire universe simultaneously. Thus it can be used as an interplanetary distress signal. Everyone would suddenly be like "holy crap, the young king isn't king anymore, send space marines!". Sagittarian Milky Way (talk) 19:30, 22 January 2022 (UTC)

The article Faster than light leads to another article called Faster-than-light communication, which in turn includes a reference to Star Trek and its postulated Subspace communication. --←Baseball Bugs ^{What's up, Doc?} carrots→ 04:33, 23 January 2022 (UTC)

January 21

Schrödinger's cat = Checking whether a coin is fair??

Why Schrödinger's cat is treated different from coin flipping? They both have 2 possible outcomes. One is treated as though experiment, other one falls under Maths. Rizosome (talk) 03:51, 21 January 2022 (UTC)

See Qubit. --Cookatoo.ergo.ZooM (talk) 05:47, 21 January 2022 (UTC)

But I am not asking units of Quantum information. Rizosome (talk) 11:14, 21 January 2022 (UTC)

The uncertainty in a coin flip can be attributed entirely to the experimenter's lack of knowledge about the physical state of affairs at the instant the coin is released, such as its precise velocity, momentum and angular momentum. Given all relevant values (which should also include the movement of atoms in the coin, the air, and the object on whose surface the coin should land), the outcome is determined by the laws of classical physics. With some effort, an experimenter can train themselves to flip a fair coin so as to produce a biased outcome; see Coin flipping § Physics. For the quantum equivalent, even if the precise initial physical state is known, the outcome is still not determined (at least, in the Copenhagen interpretation); see Bell's theorem. The uncertainty of the fate of the cat is not due to a lack of knowledge, but is inherent in the laws of physics as they are currently understood.  --Lambiam 12:01, 21 January 2022 (UTC)

It is worth noting, however, that an actual cat is a (deliberately) bad example for quantum superposition: it is always either dead or alive; undead cats do not exist in reality (see quantum decoherence for more on this). Cheers ❖ _hugarheimur 13:23, 21 January 2022 (UTC)

I understand that Schrödinger's cat and Coin flipping are not same from this line: With some effort, an experimenter can train themselves to flip a fair coin so as to produce a biased outcome; see Coin flipping § Physics. Rizosome (talk) 09:19, 22 January 2022 (UTC)

Resolved

As pointed out here, it's actually exactly the same, because all probabilities in the natural world ultimately originate from quantum fluctuations. A probability due to a lack of knowledge falls into the same category, as it's ultimately due to a lack of correlations between the brain processes that initiate a certain action and the resulting outcome of e.g. a coin flip. The randomness in the brain processes have a quantum mechanical origin. Count Iblis (talk) 21:16, 22 January 2022 (UTC)

In a game like Let's Make a Deal, in which a rational player needing to solve the Monty Hall problem should base their rational computations on probability theory, and more specifically the rules of conditional probability, the player's lack of information concerning the prize-carrying choice when offered the opportunity to switch after one choice is shown to be a dud is not due to quantum fluctuations. And if superdeterminism reigns supreme, quantum fluctuations are a mirage due to our lack of information.  --Lambiam 14:34, 23 January 2022 (UTC)

Previous answers are correct, but to emphasise: Quantum Mechanical randomness is true randomness. It is a fundamental part of the Universe. In this type of randomness, even knowing everything there is to know about a system, you cannot know with certainty the outcome of a measurement before you make it. Coin flipping is more of a perceived randomness - in a sort of chaotic way, small changes in initial conditions become large changes in the outcome, making the outcome hard to predict and thus appear as random. I might call this statistical randomness - the outcome of a coin flip is, in statistical talk, a random variable. (A subtle point is that the two coexist - the coin flip will be affected, in perhaps imperceivable ways, by Quantum Mechanical randomness.) — Jthistle38 (talk) 22:33, 26 January 2022 (UTC)

Does colored newspaper ink contain heavy metals?

I was told that the colored ink in newspaper contained heavy metals (and to keep those pages out of the garden). That was a long time ago. There is now a lot more color in the newspaper. Are they still based on heavy metals? Thank you. RJFJR (talk) 04:30, 21 January 2022 (UTC)

Not according to this source: "Today’s newspaper uses ink that is 100 percent non-toxic. Inks of all colors and black and white are included." What I see in sources^[2][3] is that volatile organic compounds are considered more of a problem than pigments, an issue that is resolved if the newspaper uses soy ink. But this source mentions cadmium yellow as a common newspaper-ink pigment; the heavy metal cadmium is toxic.  --Lambiam 12:32, 21 January 2022 (UTC)

So are non-coloured newspapers now safe for Fish and chips as they were in my youth? Martin of Sheffield (talk) 14:26, 21 January 2022 (UTC)

Perhaps if liberally sprinkled with salt and vinegar. What was considered safe in your youth may no longer be generally recognized as safe today, though.  --Lambiam 14:17, 23 January 2022 (UTC)

At the time of chips-in-newspaper (before about 1970?), they were cooked either in beef dripping (in the North of England and Scotland) or lard. Much healthier! Alansplodge (talk) 22:50, 23 January 2022 (UTC)

In the era of typesetting, the printing press probably contained heavy metals like lead, and could transfer some to the paper. Nowadays these methods are not so common. Also Phthalocyanine Blue BN a common blue pigment contains copper. Copper is an essential metal for plants. Graeme Bartlett (talk) 22:20, 23 January 2022 (UTC)

January 22

Cuboctahedral dice (D14? D6/8?)

I asked this question in Mathematics, looking for a theoretical treatment, but didn't come up with a definitive answer.

A cuboctahedron is a solid shape with six square and eight equilateral triangular faces. It could conceivably be used as a 14-sided die. By symmetry, the probability of rolling any one the the square faces is equal, likewise the probability of rolling any one of the triangular faces. It seems likely, however, that those probabilities differ from each other, so such a die would be more likely to land on a square (or maybe a triangular?) face. Has anyone ever run this as an experiment and found out the probabilities? --Verbarson ^talk_edits 23:44, 22 January 2022 (UTC)

As a first guess, I'd look at the difference in area of each face: a square vs equilateral triangle with the same edge-length. I wonder if the distance from the centroid of mass to the different kinds of faces matters, as far as a roll "settling down" to lower energy? Would be an easy experiment. DMacks (talk) 00:42, 23 January 2022 (UTC)

You could cut smooth wood with carpenter tools, use potters clay to fill and glue the mold together, rent (probably) or buy (definitely) a kiln (or say Hey school, I just met you boy, and this is crazy, but here's my number, so call me maybe to schedule a bloc of cuboctahedron baking time), bake it, remove the ashes, shake it in a large box which you've padded enough to ensure it stays an uncracked cuboctahedron then drop it on a mattress and see which shape you got. Then repeat many times till the x-sigma "real probability of square" is down to plus or minus 0.05% from the ratio you threw so far or whatever's enough to satisfy you. Of course it'd take more throws to prove fair to very high accuracy than to prove not fair in a very biased die to the same accuracy. There's likely a calculator online that tells you where the sigmas are for any ratio of square throws to triangle ones. Sagittarian Milky Way (talk) 01:02, 23 January 2022 (UTC)

Or if you happen to be more skilled with computers than with hand tools, create a software model (some maths department might have one already) and print a bunch of copies using a 3-D printer. GeorgiaDC (talk) 02:25, 24 January 2022 (UTC)

Tangential to your query, the article Dice has tables of dice with various numbers of sides that are actually manufactured. The only entry for a 14-sided die is a Heptagonal trapezohedron, a very different form from the cuboctahedron you are considering: this suggests to me that the latter would not be easy to modify and make "fair", otherwise it would be in use. {The poster formerly known as 87.81.230.195} 90.193.128.231 (talk) 04:02, 23 January 2022 (UTC)

That table restricts itself to "uniform fair dice", where symmetry forces the probability of each of n faces to be 1/n. I want to know about an explicitly unfair shape for dice. How unfair is it? Is the probability of each square face greater than that of each triangular face, but is it by less than 8⁄6 so any roll is more likely to land on a triangular face (which is my guess)? --Verbarson ^talk_edits 22:31, 23 January 2022 (UTC)

I'd guess the centre of gravity of the die is lower when it sits on a square face, and that would then be the preferred final state. Another way of looking at it would be how much does the CG have to lift to rotate around one edge. Greglocock (talk) 05:27, 23 January 2022 (UTC)

I haven't proven it, but my gut feeling is that it's more likely to fall on one of the square faces, but the exact ratio may depend on the elastic properties and friction of the die and the surface on which is bounces. With more damping, I expect the square faces will be less favoured. So if you want to know, that's something to look into. PiusImpavidus (talk) 11:56, 23 January 2022 (UTC)

The only feasible way to find out for sure is the experimental way (which may turn out to produce different results depending on the details of the experimental set-up).  --Lambiam 12:58, 23 January 2022 (UTC)

What are the elastic properties and friction of craps dice following the rules of Vegas craps and what are cheaper ways of getting close without having to buy a casino-grade craps table and commission casino-quality cuboctahedral dice from whoever makes those? Sagittarian Milky Way (talk) 16:29, 23 January 2022 (UTC)

This is just a rough sketch. First, define what you mean by landing on a face: do you require friction to take away all kinetic energy, or is it good enough as long as any bouncing doesn't change which face is 'down'--in which case you should define what that means as well. Of course, without friction and with enough energy, the die might bounce around changing face forever, but maybe on the lower end, the amount of kinetic energy required to turn over a triangular face is different from that for a square face, and you can still make a quantitative comparison. Second, analyze how likely it is for a die to contact the floor at a vertex, along an edge, or flat on a face (some of these might be negligible depending on how you simplify your approach). For any such contact scenario, further analyze where the die would go from there depending on its momentum. Finally, tabulate the probabilities for 2 categories of outcomes--(1) die lands in a way with such energy that a triangular face is 'down', either at rest or oscillating along that face's edges and vertices, and (2) similarly for a square face. The probabilities might not add up to 1 because of possible existence of other scenarios, but at least you can compare the two. GeorgiaDC (talk) 20:47, 23 January 2022 (UTC)

Even with a sophisticated physical model that fixes parameters for the shape of the die (size, edge rounding), its mass and Reynolds number, the air and surface friction, and the elastic moduli of the die and surface materials, an unknown factor of paramount importance remains: the distribution of the initial state in the state space of states the die can be in (height, orientation, and linear and angular momentum). For the directions of the orientation and the momenta we can use a uniform distribution over the unit sphere, but there remain three scalars (height and the magnitudes of the momenta) with no plausible candidates for their distribution. I conjecture that if we use one-point distributions and let their centres grow without bounds, the distribution of outcomes of the die throws approaches a limit.  --Lambiam 13:21, 24 January 2022 (UTC)

Thinking a bit more about the effect of the initial state, I realized that as the release height grows – unless the other scalars grow exponentially with it (which in reality would cause the die to melt) – the velocity of the die on first impact will approach more and more terminal velocity in a vertical direction. On one hand, one might expect it to assume an orientation that minimizes drag; but, on the other hand, its wake will be turbulent and I'm not sure if that results in an irregular but strong rotational force. In any case, the limit behaviour as release height goes to infinity may not be "typical" for dice loosely thrown out of a player's hand.  --Lambiam 21:38, 24 January 2022 (UTC)

I figured there needs to be a lot of simplifications to even a theoretical model. For example, there would be no dropping from height, only imparting angular momentum to the die before allowing floor contact with negligible drop. Constant gravity. Perfect elastic collisions. No friction. I might even assume that any initial state is already floor contact along an edge of a face (triangular or square) at some angle. Then I might calculate how much angular momentum is necessary to overturn that face versus oscillating under a restorative gravity force. Finally, tabulating the results for all such edges, angles, and angular momenta, and see by how much the likelihood differs between settling on a triangle vs settling on a square. If one's more ambitious, can add linear momentum and static friction (only for rolling calculations, no damping/dissipation effects) as well. Although by this point, it's probably easier to gather empirical data instead by 3-D printing a die and rolling it under some setup. GeorgiaDC (talk) 05:29, 25 January 2022 (UTC)

Here is a thought that should be "unsettling" (LOL). With perfect elastic collisions and no friction, there is no energy loss, so the die keeps bouncing forever. As to the suggested simplification for the orientation at initial contact with the floor, the most likely case is with just one corner (vertex) touching the floor; for idealized dice with unrounded edges and corners, when in a uniformly random orientation, the other cases (a whole edge or even face) almost never occur.  --Lambiam 08:02, 25 January 2022 (UTC)

I think not necessarily. If initial energy isn't sufficient, the die can rock back and forth, revolve or even bounce about the same face. Cases of "down" face changing forever do not have to be included for comparison (triangle vs square). And say, only corners make contact at first, ignoring edges or faces. There is only a finite number of them, so should be able to analyse in some form. Notice also that in cases where there's no bouncing but only rolling, after an initial corner contact, I get the feeling that what follows is probably an edge contact. GeorgiaDC (talk) 10:12, 25 January 2022 (UTC)

As could be expected, the problem has been considered before.^[4] Letting p stand for the probability of the die settling on a square face, an experiment with a cardboard cuboctahedron in a run of 100 trials reportedly gave a value p ≈ 0.8 with σ ≈ 0.04. The proposer gives a mathematical solution based on the assumption that at some point the die stops tumbling or sliding but is then still rolling, turning along its edges from face to face. Each turn is from a square to a triangular face or vice versa, and the two require different kinetic energy levels; when insufficient for a next turn, the die settles. As the die tumbles, it loses energy in a somewhat unpredictable way; assuming a uniform distribution of the kinetic energy from 0 to a level in which the die must turn anyway, the proposer obtains p = 0.76239..., close enough to the experimental result. In an exact formula,

$p={\frac {~\,\,9+6{\sqrt {2}}-4{\sqrt {3}}-3{\sqrt {6}}}{10+6{\sqrt {2}}-4{\sqrt {3}}-3{\sqrt {6}}}}\approx 0.76239\,.$

(The fraction of a cuboctahedron's surface area contributed by its square faces is only ${\tfrac {1}{2}}(3-{\sqrt {3}})\approx 0.63397\,.$)  --Lambiam 10:01, 25 January 2022 (UTC)

January 23

Exceptional configurations

I was puzzled by the fact that chromium and copper have five and ten electrons in 3d orbitals rather than four and nine. Now I have come to know from Dr. Wayne Breslyn's video that half-filled or completely filled d orbitals are more stable than those with one electron less. However, I found a few more exceptions in 4d orbitals, i.e., niobium, ruthenium, rhodium, and palladium, which are neither half-filled nor completely filled. What may be the explanation for the exceptional electronic configuration? Huzaifa abedeen (talk) 06:32, 23 January 2022 (UTC)

Check out the article on Aufbau principle. The "Exceptions" headings are particularly relevant. Search the web for Madelung rule exceptions. The neat math rules for calculating atomic shells do not work in all cases in the real world. The math is an approximation that does not always match real world experiments. If you can find the quantum (and beyond that) physics answer, please do write an article here about it. Perhaps even collect your Nobel Price when you do that. 85.76.87.150 (talk) 15:57, 23 January 2022 (UTC)

Atomic orbital and electron configuration also have some useful information. As they discuss, when you start getting to large atoms with complex orbitals, the energies of different subshells can be very close or overlap. Nature always tries to fill the lowest-energy subshells first. There are also complicated effects that can come into play from electron-electron interactions, with electrons of different orbitals repelling each other (due to their negative electric charge) or one orbital "screening" the positive charge of the nucleus from another. --47.155.96.47 (talk) 05:04, 25 January 2022 (UTC)

"Nature always tries to fill the lowest-energy subshells first" as the whole statement, with then a bunch of exceptions and such, leads to my students thinking Nature is mostly exceptions. Instead, "Nature always tries to reach the lowest overall energy configuration." Then there are just a set of details what causes higher vs lower energy. DMacks (talk) 05:34, 26 January 2022 (UTC)

How different type of species were discovered before 1970s?

Omicron virus discovered through Genome Sequencing method used not before 1970s. How different type of species were discovered before 1970s? Rizosome (talk) 06:41, 23 January 2022 (UTC)

Please note that the Omicron variant is not considered a species of its own, but one of the variants of the SARS-CoV-2 species. Our article Virus classification explains how viruses are classified as species, most of which does not depend on genome sequencing but can be done by inspecting electron microscope images (for the phenotypic characteristics) and observing its macroscopic effects (host organisms and disease symptoms).  --Lambiam 12:47, 23 January 2022 (UTC)

As the virus classification article states, the classification of viruses can be inconsistent and is very much an unsettled question. This is on top of the more general uncertainty of the species concept. People like nice, neat classifications with exact places to put everything and consistent rules for doing so. Nature is a LOT messier. --User:Khajidha (talk) (contributions) 16:07, 23 January 2022 (UTC)

Messy as it may be, such classifications may have a practical usefulness, from conservation efforts for vulnerable species to developing effective medication for diseases with identifiable pathogens.  --Lambiam 21:58, 23 January 2022 (UTC)

"Conservation efforts for vulnerable species"? I think the vulnerable species is man, not some <nasty word> virus! Martin of Sheffield (talk) 22:02, 23 January 2022 (UTC)

I reacted to a contribution referring to "the more general uncertainty of the species concept" – which even applies to proposed extinct (sub?)species in the genus Homo.  --Lambiam 13:39, 24 January 2022 (UTC)

Along with the ongoing question about whether viruses are really "alive" or not. --←Baseball Bugs ^{What's up, Doc?} carrots→ 16:51, 23 January 2022 (UTC)

This line solved my doubt: Our article Virus classification explains how viruses are classified as species, most of which does not depend on genome sequencing but can be done by inspecting electron microscope images (for the phenotypic characteristics) and observing its macroscopic effects (host organisms and disease symptoms). Rizosome (talk) 07:04, 24 January 2022 (UTC)

Resolved

Adhesive for use on skin

I mean the stuff on band-aids and adhesive tape, not surgical adhesive. Any idea what it is that they use, and where to get it? Somehow separating it from adhesive tape might be a possibility if there's no other way. Application is strapless n95 masks, which stay on with adhesive (look up "Readimask"). They apparently work pretty well on first use, but aren't easily re-usable because the adhesive loses its stickiness. Thus, the is to find a way to add more. The masks seem like a nice idea but they are on the expensive side. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 08:11, 23 January 2022 (UTC)

Our article Adhesive bandage has this to say: "The adhesive is commonly an acrylate, including methacrylates and epoxy diacrylates (which are also known as vinyl resins).^[2]"  --Lambiam 12:53, 23 January 2022 (UTC)

Thanks, I should have looked there. I also found a less expensive source of strapless masks. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 02:26, 24 January 2022 (UTC)

January 24

Why were much of Japan's deciduous forests replaced with conifer plantations?

As mentioned in the article Japanese wolf. What purpose do the plantations serve? ZFT (talk) 06:48, 24 January 2022 (UTC)

Not sure it gives a good reason, but see Afforestation in Japan#History for some background. Clarityfiend (talk) 07:32, 24 January 2022 (UTC)

This chapter titled "Japanese Forestation Policies During the 20 Years Following World War II" gives an explanation:

During World War II, the area cut annually in Japan exceeded the area planted, and cutover land was common. Within approximately 10 years of the end of the war, however, forestation on cutover land was almost complete. In the 10 years that followed, forestation policies targeted increasing coniferous tree plantations to secure industrial roundwood. Forestation plans and legal systems were developed, and organizations such as the Prefectural Forestry Corporations and Forest Development Corporation were founded to promote the planting of coniferous trees.

Clarityfiend (talk) 07:36, 24 January 2022 (UTC)

"The softwood derived from conifers is of great economic value, providing about 45% of the world's annual lumber production. Other uses include the production of paper and plastic from chemically treated wood pulp." (Quoting Conifer#Economic_importance.--Shantavira|^{feed me} 09:12, 24 January 2022 (UTC)

A similar drive for domestic softwood production in the UK (in this case following WWI) resulted in the Forestry Commission. Alansplodge (talk) 09:44, 24 January 2022 (UTC)

drum in front of a military military (WW I)

What is the name and the purpose of this "oil barrel" mounted in the very front? --Mateus2019 (talk) 16:56, 24 January 2022 (UTC)

It is probably a mine roller. Nimur (talk) 17:32, 24 January 2022 (UTC)

(ec)Not sure about the drum but it appears to be a Somua MCG-4 or MCG-5 artillery tractor (or possibly an earlier version). Lots of descriptions of this vehicle but I can't find an explanation for the drum. Mikenorton (talk) 17:38, 24 January 2022 (UTC)

Also found on other half-tracks, such as the M3 and the Unic P107 (File:Unic P107 , Musée des Blindés, France, pic-2.JPG). Mikenorton (talk) 17:53, 24 January 2022 (UTC)

Explanation with useful diagram found here, to quote "the roller worked to prevent the front bumper from digging in when at too severe of an angle of approach. Its contact would lift the front wheels". Mikenorton (talk) 18:59, 24 January 2022 (UTC)

• And it turns out that WP:WHAAOE wins again - see unditching roller. Mikenorton (talk)

Thanks Mikenorton! I agree, it's more likely to be an unditching roller (it's positioned a little close to the engine-block to be useful as any kind of mine flail or mine roller). Nimur (talk) 20:12, 25 January 2022 (UTC)

Ice age meat conservation

I read long ago maybe in Scientific American about archeology, maybe in the USA or Canada, where they escavated a well or shaft finding some vertical pole and round each pole several rather heavy stones. They reconstructed it so, that hunters in the past were filling intestines of some large game with meat and some stones, then wrapped the filled intestines round some poles inserted under water in a pond, the stones helping to sink the meat. The cold water would conserve the meat for several months, maybe helping lactic fermentation.
I cannot find references any more. Can you help please? Thank you. 2003:F5:6F0E:8B00:4002:87CF:C1C1:20DB (talk) 22:00, 24 January 2022 (UTC) Marco PB

It wouldn't work for long in the current summer climate of central USA but in places or ice ages when the average annual temperature is colder, like fridge or freezer cold, then the very bottom of a deep enough water body might be the temperature of the densest temperature of water (4°C). If it is very deep like contemporary Lake Superior the acceptably cold layer thickness might be many many meters. Sagittarian Milky Way (talk) 02:58, 25 January 2022 (UTC)

That doesn't sound like a very effective way to preserve meat. Maybe I'm misunderstanding what you're describing? If you left the meat hanging in an empty, dry well or shaft, especially if it had been initially smoked or salted, you would have a kind of larder. But if you then put that meat into a pond, all you'd end up with is some very happy fish. Matt Deres (talk) 14:53, 25 January 2022 (UTC)

Depends if you can make fish unwilling or unable to pierce intestines or not. With mammals you can coat it with sticky high-capsaicin stuff, with birds that doesn't work, with fish I don't know. And maybe whether you make the intestines waterproof is important too. And if you can MacGyver a vacuum pump with a mouthpiece and one-way flap or something maybe even better. Sagittarian Milky Way (talk) 15:38, 25 January 2022 (UTC)

The OP is asking about an archaeological site; what are you going on about with vacuum pumps and capsaicin? Matt Deres (talk) 19:39, 25 January 2022 (UTC)

If you have a Stone Age way to deter animals from underwater meat intestines that would be more realistic. Maybe there's a way, some gardeners deter herbivory with a dried blood bag from the garden store (USA deer don't want to eat anything that smells like a light dusting of pulverized blood) Sagittarian Milky Way (talk) 20:51, 25 January 2022 (UTC)

Thank to everyone. Someone tried actually and let some meat in a pond under cold water and it was still edible after several months, althought with an unusual smell (but people eat Surströmming, don't they?). On the other side I don't think fish to be a real problem in isolated subglacial bog ponds.

But yes, I was looking for references about this particular archeological site, but it was no full article but instead a short message under news so it is not a surprise even googl doesn't know of it. 2003:F5:6F0E:8B00:B4DB:248B:38E7:9C7E (talk) 20:33, 25 January 2022 (UTC) Marco PB

Is it anoxic down there? That might help. Sagittarian Milky Way (talk) 20:51, 25 January 2022 (UTC)

It occurred to me too, that the anoxic environment deep in the water of a pond could be relevant, I'm thinking for example about the so called Bog Bodies, dead people or animals conserved during up to some millenia in the anaerobic, acidic environment of peat bogs. But how far they are still edible is an open question. 2003:F5:6F0E:FD00:3110:6631:C3BB:E9DB (talk) 17:47, 26 January 2022 (UTC) Marco PB

Anecdotally (meaning I haven't looked for references), it seems to be the case for some samples of Bog butter. {The poster formerly known as 87.81.230.195} 90.213.224.157 (talk) 18:15, 26 January 2022 (UTC)

You have it. That could be a practical solution for the European surplus butter problem. 2003:F5:6F14:DE00:D0F0:4D6E:90B2:D717 (talk) 17:53, 27 January 2022 (UTC) Marco PB

January 25

What technology used in Bluetooth?

In Bluetooth it says: Bluetooth uses a radio technology called frequency-hopping spread spectrum. 

But in Phase-shift keying, it says: It is widely used for wireless LANs, RFID and Bluetooth communication.

Is it PSK or Frequency-hopping spread spectrum? Rizosome (talk) 07:30, 25 January 2022 (UTC)

Our article on Bluetooth also says "Originally, Gaussian frequency-shift keying (GFSK) modulation was the only modulation scheme available. Since the introduction of Bluetooth 2.0+EDR, π/4-DQPSK (differential quadrature phase-shift keying) and 8-DPSK modulation may also be used between compatible devices". Someone like Nimur could explain better I'm sure but AIUI, there's no contradiction here since these don't refer to the same thing Bluetooth uses FHSS and either PSK or FSK. Similarly Bluetooth Low Energy uses DSSS and FSK. Nil Einne (talk) 09:44, 25 January 2022 (UTC)

Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral band. Phase-shift keying (PSK) causes modulation sidebands close to the carrier frequency but is not itself a spread spectrum method. Philvoids (talk) 18:09, 25 January 2022 (UTC)

I think we have to disentangle the terminology: "spread-spectrum" can be used as a qualitative description of the frequency behavior, and this description can be applied (qualitatively) to many different kinds of transmissions.

From this perspective, the description "spread-spectrum" is not exclusive of other descriptions: any particular scheme can be both PSK and spread spectrum.

At the same time, "spread-spectrum" can be used to specify a particular technical detail about a particular piece of the technology implementation.

Whether BlueTooth actually satisfies either adjective might depend on who you ask. But of course, this is the reference desk - so we have to find a reliable source! The canonical, authoritative source is the BlueTooth SIG (Special Interest Group); they publish most of their detailed technical specifications and basic technology summaries at zero-cost.

From Learn About BlueTooth - Technology Overview - the set of technologies branded as "Classic" BlueTooth are described in this way:

• Channel Usage - Frequency-Hopping Spread Spectrum (FHSS)
• Modulation - "DQPSK" (and others)

So the distinction about which adjectives they apply depend on which layer of abstraction you're evaluating. Like everything in modern wireless communication, it helps to think about the radio as part of a protocol stack: and BlueTooth is a sophisticated stack! The low level radio control layers - those portions that select the frequency - are conceptually different from the slightly-less-low-layer radio modulation control, where the encoding or "keying" scheme is implemented. And these are, in the common model-abstraction, at a "lower layer" than the BlueTooth communication protocols that sustain various higher-level features. If you're looking at the signal strictly in the context of its radio frequency spectrum, you'll probably see big bursts of noisy energy - it'll be challenging to describe the power-spectrum at all, because that spectrum will vary as many system-parameters change. Even the keying-scheme can be changed during normal use.

Nimur (talk) 20:27, 25 January 2022 (UTC)

So both PSK and Frequency-hopping spread spectrum (FHSS) are used in bluetooth technology? Rizosome (talk) 00:59, 26 January 2022 (UTC)

Yes, much the same as both motors and wheels are used in car technology. They serve different functions.  --Lambiam 09:20, 26 January 2022 (UTC)

I got the answer from this line: Yes, much the same as both motors and wheels are used in car technology. Rizosome (talk) 06:51, 27 January 2022 (UTC)

Resolved

Solar panels silicon nitride coating

Hi, I've been reading and searching for information related to solar panels made of monocrystalline silicon. I read about silicon nitride coating. I'm sure that such a coating must have it's disadvantages (material-wise), such as degradation over time. The problem is that I can't find any specific source for explanations - I can't point out those problems With proper information. I would appreciate your help 87.70.11.210 (talk) 16:56, 25 January 2022 (UTC)

Monocrystalline silicon and silicon nitride are very different things. Are you asking about the pros and cons of using silicon nitride coatings in general, or for using them specifically on solar panels (presumably in comparison to other ceramic coatings used for solar panels), or even more specifically on solar panels made of monocrystalline silicon?  --Lambiam 09:41, 26 January 2022 (UTC)

I'm specifically interested in the pros and mostly cons of using silicon nitride coatings on solar panels made of monocrystalline silicon. No need for comparisons :) 87.70.11.210 (talk) 13:40, 26 January 2022 (UTC)

Here are a few links to research articles: [5], [6], [7], [8]. An issue mentioned in some articles on silicon nitride coatings in general, not in connection with solar panels, is a difficulty in applying them by conventional thermal spray processes, due to silicon nitride decomposing under a high temperature (2173 K). However, other spraying processes appear to work well.^[9][10] Benefits mentioned by a firm that has a financial interest in the issue (but not contradicted by others) are low density, high temperature strength, superior thermal shock resistance, excellent wear resistance, high hardness and toughness.^[11] Si_xN_y coatings subjected to micro scratching have been reported to undergo adhesive failure with loads above 214 mN;^[12] I have no idea if that signals high durability.  --Lambiam 21:44, 26 January 2022 (UTC)

Spin states of planets in S-type circumbinary orbits

Wikipedia defines "S-type" orbit as follows: When you have a binary star i.e two stars (here called "A" and "B") in a common orbit, a planet (here called "b") that has its own orbit around just one star (hereby called "B") is an "S-type planet" [in contrast to "P-type planets" which have an orbit around both "A" and "B"]. I have been looking for research on how tides would influence the spin state of planet b when it is close enough to B that tidal acceleration would play a role, but where the gravitational influence of "A" cannot be disregarded. I can't find any research that discusses the scenario of a S-type planet. Jo-Jo Eumerus (talk) 17:08, 25 January 2022 (UTC)

If the gravitation of A is so strong that effects the rotation of the planet then its orbit is likely to be unstable. Ruslik_Zero 20:39, 25 January 2022 (UTC)

Hair Loss Restoration

Biotin, or Vitamin B7, is a natural substance frequently touted for restoration of hair loss or for increase in density of hair. In the footnotes to the Wikipedia article explaining it are two references (footnotes 29 and 34) regarding studies of subjects to evaluate the efficacy of Biotin for this purpose. One of those footnotes refers to a product called Viviscal which was found effective in restoring hair loss for women but when I searched Wikipedia for Viviscal no such page is found. I and perhaps many others would like to know what Viviscal is and where to find it. Probably millions would thank you.Bruce1939 (talk) 20:41, 25 January 2022 (UTC)

Wikipedia is not for product advertising. However, a Google search brings up lots of stuff, e.g. the Healthline article Viviscal Hair Growth Treatment: Does It Really Work? Clarityfiend (talk) 22:08, 25 January 2022 (UTC)

January 26

Maximum no. of compounds

The elements which form the most compounds are carbon, which most of the compounds of carbon have hydrogen in them, and hydrogen, which is the element which can form compounds with almost all of the elements in the periodic table. If hydrogen forms the maximum number of compounds, why is a whole branch of chemistry dedicated to the compounds of carbon? Maximum number of compounds are formed by Which element? Carbon, hydrogen, or any other Huzaifa abedeen (talk) 06:17, 26 January 2022 (UTC)

Organic chemistry is interesting because of its practical applications in biological processes. "Life chemistry" is also something of a historical accident, as in the past people held the idea that living matter had some kind of a mystical life force that made it fundamentally different from non-living matter.

We could invent a specific field of study of hydrogen for purely intellectual interest, and invent a name for that, but what can be said about hydrogen is already pretty well covered by general chemistry.

The number of different molecules that can be formed is pretty much an open-ended question because there are big molecules that can not be readily counted, such as DNA and proteins and other macromolecules. 85.76.87.150 (talk) 08:52, 26 January 2022 (UTC)

Structure of ethanol

(edit conflict) If you look at the structure of compounds, like that of ethanol or benzene, you can see that the carbon atoms can form chains and rings, and thereby the backbone of a compound. Hydrogen can only appear as fringe.  --Lambiam 09:14, 26 January 2022 (UTC)

Per Lambiam for the same reason that the study of human biology spends more of its energy on your internal organs than your hair, organic chemistry is more concerned with the carbon than the hydrogen. The carbon provides the primary structure and function of organic molecules, while the hydrogen, while there is a lot of it, is just kinda "there". You have more hairs than hearts, but I dare say your heart's function is more vital to your life than that of your hair. --Jayron32 11:51, 26 January 2022 (UTC)

85.76.87.150, if you think that living and non-living matter are not fundamentally different, I suggest you do some more reading. Start with life. -- Jack of Oz ^{[pleasantries]} 21:40, 26 January 2022 (UTC)

See Wöhler synthesis, in particular the "Debates" section. See also Vitalism. Martin of Sheffield (talk) 21:50, 26 January 2022 (UTC)

As Martin implies above, there is nothing special about the atoms, compounds, molecules, etc. that make up living things that makes them different than the exact same molecules as made from non-living sources. If you created DNA from carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur atoms, each of which came from non-living sources, then that DNA would behave exactly like DNA created inside of your cells. The now long-debunked theory that there was some special "life force" that made living matter somehow different from non-living matter is called vitalism, and it's not a thing. The work of Friedrich Wöhler and Hermann Kolbe put an end to that thinking. --Jayron32 12:49, 27 January 2022 (UTC)

Sure, life is different from non-life. Life has, depending on your definition, properties such as (1) birth, (2) death, (3) metabolism, (4) reproduction. The definition differs depending on who you ask.

If you send a probe to Mars to find "life" you need to think pretty hard about what that word means, and how to differentiate between "life" and "non-life" ground samples.

But at the molecular lever making a stand between living and not-living molecules is magical thinking. Compounds that contain carbon are not magically different those that do not.

Thank you for your suggestion of "doing more reading". I genuinely non-sarcastically do try to do that. 85.76.87.150 (talk) 17:01, 27 January 2022 (UTC)

The CAS database has at least 3 orders of magnitude more carbon compounds than non-carbon. Sagittarian Milky Way (talk) 21:59, 26 January 2022 (UTC)

Carbon § Compounds: Carbon is so special because carbon atoms can bind to each other to form long chains, and these bonds between carbon atoms are strong and stable. This is why all known life is based on carbon chemistry. No other element can do this to the degree that carbon can. At Earth surface conditions, the only stable hydrogen-only compound is dihydrogen, a gas. --47.155.96.47 (talk) 00:46, 27 January 2022 (UTC)

The strong desire to form 4 bonds, ability to bond the most common non-hermit atoms in the universe (H=1 C=4 N=3 O=2) and semi-common FClBrI (1 bond) and PS (multiple) atoms, and the ability for 1 or 2 or 3 or even "1.5" of those bonds to be used up on the same atom pair also help. Sagittarian Milky Way (talk) 01:57, 27 January 2022 (UTC)

Tar sands tailings

Which metals are concentrated to a significant degree in the tailings from tar sands processing? In particular, do they contain high levels of metals from groups 4-6, 12 and 14? Is there a comprehensive list of metals in tar sands tailings somewhere out there? 69.181.91.208 (talk) 12:41, 26 January 2022 (UTC)

It would, of course, depend on which tar sands are being looked at, but this has some promising leads to help with your research. --Jayron32 12:44, 26 January 2022 (UTC)

January 28

Why characteristics graphs of p–n junction and Zener diode are similiar?

See characteristics graphs of p–n junction : click here

See characteristics graphs of Zener diode : click here Rizosome (talk) 01:49, 28 January 2022 (UTC)