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July 8

Speed of Light - Formation of images

We can see light via our eyes either directly or if it reflected off from the object.

Sunlight reaches earth.jpg Sunlight takes an average of 8 min and 20 sec to reach the earth. The speed of the light is 299,792 kilometers per second.

The sun is 109 times bigger than the earth. It radiates light in all direction. Earth receives a very small fraction (less 1% of the sunlight - guess). We are unable to see the rest of the sun lights as it fall in the space-like region and their direction of traveling keep them away further in the space-like region of light-cone - true. Therefore

How come we are able to see the full image of the sun when more than 99% of the sunlight doesn’t even fall on the earth (falls away into the space-like region of the light cone)? No reflections involve either – And the same is applied to the stars, galaxies, and image of the BH, etc.

Would the interference of light rays from these cones nullify the formation of shadows on earth? — Preceding unsigned comment added by Eclectic Eccentric Kamikaze (talk • contribs) 03:56, 8 July 2019 (UTC)

For an accurate idea of how the Sun emits light, you must keep in mind that rays of light do not only emit perpendicular to its surface (as if it had a smooth surface anyway). Every point on the surface of the sun is emitting light in every outward direction. We can see the whole of the sun because for each part of it that we can look at, some light rays are being emitted from that part toward our direction. Someguy1221 (talk) 04:01, 8 July 2019 (UTC)

1)far less than 1%. More like surface of the Earth disc / area of a sphere which radius is the sun-earth distance πR²/4πD², were R=6,371 and D=149,598,023. That is, less than 0.5 e-9 (half a billionth)

2)well, because that the definition of an image. Why would you need to see all the light emitted/reflected? a small fraction will do, as evidenced by the possibility to get image by photographing, when the collected light comes a fraction of a second. And it apply just as well to a computer screen or a chair in front of you. Gem fr (talk) 06:42, 8 July 2019 (UTC)

3)interference have requirement, which are explained here; Wave_interference#Light_source_requirements. These are not met as far as the sun is concerned. To be more precise, they are met by a so small fraction of the sunlight, that we cannot see any difference. Gem fr (talk) 06:42, 8 July 2019 (UTC)

Not a satisfactory answer (to me) but still, it's not 100% guarantee that we would get the same amount of light especially its distribution throughout the year when the earth orbit around the sun, therefore, shouldn’t the sun change its shape with the passage of time? — Preceding unsigned comment added by Eclectic Eccentric Kamikaze (talk • contribs) 04:47, 8 July 2019 (UTC)

in fact we DON'T get the same amount of light throughout the year when the earth orbit around the sun. The so called solar constant is not really a constant, as physicists define them. Gem fr (talk) 06:42, 8 July 2019 (UTC)

If you're talking about the sun changing shape due to perspective, no for two reasons: A) The sun is approximately a sphere, and so its projection is a circle from any distance; B) the distance from the Earth to the Sun does not change that much over the course of the year, only a few percent. I think you need a better idea of your own idea. Make another diagram, but trace every light ray that reaches your earth-bound observer from the sun. Try to figure out what that means, and then come back here if you still have questions. (Okay, not literally every light ray, but get the whole range of angles from which they will reach your observer.) Someguy1221 (talk) 21:37, 8 July 2019 (UTC)

It’s just a tentative diagram for the purpose of understanding only. I’m talking about the same image and appearance of the sun, which is like disc over the period of time. No problem with light rays fall directly on earth but it is the intensity, distribution etc of the rest of the sunlight or rays especially coming from the edges at angle that fall on earth and finally reach our eyes over the course of time which are not constant but changes due to rough surface of sun as you said. Please disregard the earth-sun distance. Anyway, thanks and I appreciate all replies. — Preceding unsigned comment added by Eclectic Eccentric Kamikaze (talk • contribs) 23:30, 8 July 2019 (UTC) For more simplicity, the dark spots (spots from where we don’t receive light rays) on the surface of the sun should increase if we see away from the center of the sun. Since the surface of the sun is not smooth therefore these dark spots should also change their position on the surface of the sun with the passage of time. Similarly, light rays that fall on earth at an angle would nullify shadows either fully or partially due to their cancellation effect. I’m not sure if we are on the same page but this is my thinking, which may be wrong, and again thanks. — Preceding unsigned comment added by Eclectic Eccentric Kamikaze (talk • contribs) 01:21, 9 July 2019 (UTC)

Hi Eclectic. I'm actually not clear on what you are thinking. That's why I suggested drawing a more complete diagram of your thoughts. Words can only convey so much. Someguy1221 (talk) 01:50, 9 July 2019 (UTC)

What darks spots? The sun is extremely bright. Sunspots only look sort of dark because they emit less light than their surroundings. But if you want a clearer idea of what's happening, you could make yourself a pinhole projector like folks often do during eclipses. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:15, 9 July 2019 (UTC)

Like my fellow Wikipedians above, I (speaking as an ex-astronomer) do not find your attempts to describe your thoughts at all clear, but with reference to your last entry you might find the article Limb darkening relevant. I suspect, however, that you have some fundamental misunderstandings about how light behaves, in which case a careful study of the material in at least the opening paragraph of Geometrical optics might help. {The poster formerly known as 87.81.230.195} 2.122.177.55 (talk) 02:22, 10 July 2019 (UTC)

As the first responder said, the surface of the sun is not smooth. it emits light rays in many possible different directions but it can’t emit light rays from the same spot in all directions at the same time as shown in figure - Right

Roughness of the surface area of the sun changes every moment. Similarly, roughness on the surface of sun is not uniform but varies vertically as well as longitudinally in all directions every moment all over the surface area of the sun.

So there are chances that some spots on the surface of sun don’t send light rays towards earth at some moments.

No light from these specific spots towards earth means no images of these spots on image of sun on earth

No image means – these spots are *dark (just like if we close our eyes) however they are ON and OFF depend upon the formation and deformation of the roughness of the surface with time and location of the earth in its orbit.

Portion “A” of the figure shows the surface area of the sun from where earth receives sunrays directly – straight, though at an angle because of the expansion of cone at every moment formed by two adjacent rays – This central part (Portion “A”) is the brightest part of the image of sun. Theoretically one light ray is perpendicular to the earth at noon if both the earth and the sun are perfect spheres. Rest of the light rays fall on earth at an angle.

The chances of the light rays that emit around the central portion A and at the edge or near edge of the sun (disc type) are low to fall on earth as compared to the light rays that emit at or near the centre of sun /disc.

Similarly, an earth can be seen from different faces (NEWS) of the sun when it orbits around the sun therefore difference in roughness means both the seen (emit light towards earth) and unseen (emit light but not towards earth) spots change their positions on the surface of the image of sun w.r.t to the earth, time and earth’s location in orbit. This makes the image of the sun sometimes dark, sometimes darker sometimes brighter but less bright as compared to the brightest central portion of the sun/disc as we receive less light to zero amount of light rays from this portion.

If aforesaid is true then the overall image of sun (disc-like) is brightest at center. Brighter to darker with dark spots may be sited around the brightest central portion toward the edge at any particular moment. i know none of you would agree but this my personal perception of the roughness of the sun as you said. — Preceding unsigned comment added by Eclectic Eccentric Kamikaze (talk • contribs) 01:14, 13 July 2019 (UTC)

The combined view of the figure (Top, North, South, NE and SE) shows there is always light from all thses direction from sun at any point on earth during day time when we see the full image of the sun which cancel the shadows either fully, partially or not at all on earth depend upon the light falling from those views. Again my personal perception about the roughness of sun if true.

Liquid Glass

I was told by a trained Stain Glass Window maker that during his tutelage he was taught that glass in its natural room temperature state is in fact a liquid. Though this is a little known fact. The reason this was taught to him was that he would need to measure any glass he had created and to in-lay it with the thickest side pointing up once installed. This would allow the glass to flow, though very slowly, over hundreds of years to be thicker at the bottom. If laid the other way around with the thickest side down, the glass would last a much lower amount of time. What truth is there in this please? Is glass at room temperature a liquid, which flows to fill any container it is in, albeit be slowly. In line with this, where is the cut off point for a liquid to be termed and considered a liquid, how long should it take to fill a contain or flow? Like mud, it can be made to fill a container but can also be made to stand on its own. Thanks Anton 81.131.40.58 (talk) 13:42, 8 July 2019 (UTC)

It's not true. "The notion that glass flows to an appreciable extent over extended periods of time is not supported by empirical research or theoretical analysis". Please see Glass#Behavior_of_antique_glass.--Shantavira|^{feed me} 13:53, 8 July 2019 (UTC)

(edit conflict) :Glass is an amorphous solid; the "cathedral glass flow" (liquid glass) theory and contradictory evidence is discussed here: Glass #Behavior of antique glass. However, according to Philip Warren Anderson: "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition." —2606:A000:1126:28D:48F3:EC22:BDAE:8519 (talk) 14:09, 8 July 2019 (UTC)

"Liquid glass" is also listed at List of common misconceptions#Materials science. Tigraan^{Click here to contact me} 15:55, 8 July 2019 (UTC)

It is not wrong to consider amorphous solids (including glass) to be liquid-like, since they share traits: Structure of liquids and glasses.

I recommend Viscosity#Amorphous_materials and Viscosity#In_solids. here is an interesting quote

many "solids" (even granite) will flow like liquids, albeit very slowly, even under arbitrarily small stress. Such materials are therefore best described as possessing both elasticity (reaction to deformation) and viscosity (reaction to rate of deformation); that is, being viscoelastic.

Yes, even granite will flow (which will help understand the wonderful fit of old stone wall, btw)

Gem fr (talk) 14:49, 8 July 2019 (UTC)

So will metals. One of the few things that actually behaves like we imagine a solid should behave is a crystal. SinisterLefty (talk) 03:13, 9 July 2019 (UTC)

@SinisterLefty: Please define "crystal", because most metals are crystals (mono- or polycrystals) by the scientific definition of the term (they show a periodic arrangement of atoms at the microscopic scale). Tigraan^{Click here to contact me} 11:54, 9 July 2019 (UTC)

Let's try "single-cell crystals with ionic bonds or covalent bonds (so not metallic bonds)". I may need to refine that further, but I think that's the general idea. It's generally between the cells in multi-celled crystals where the deformation occurs. SinisterLefty (talk) 13:45, 9 July 2019 (UTC)

Just as an aside, back in 2007 a full professor of chemistry lecturing me and the other students in my 3rd year chemistry major cohort regurgitated the "glass is a super cooled liquid at room temperature" line citing the flow of centuries old stained glass windows in cathedrals. I already knew at the time that it was a discredited pop-sci notion. After class I pointed him to the refs on the wikipedia page which explained it was wrong. He steadfastly maintained that it was a fact. This was in a physical chemistry class at a major Australian university. 202.155.85.18 (talk) 01:33, 11 July 2019 (UTC)

Most effective spending on the environment

Are there serious (science-based!) cross-disciplin recommendations about how to most effectively spend money on the environment? Essentially like GiveWell, but for the environment?

I read a few years back in the news that a groups of scientists (?!) was annually (?!) asked how to best spend a considerable amount of money (100 billion??)... but I don't find it anymore. Anything of that sort or related recommendations.

(Obviously any such recommendation would need to seriously debate what they consider "the environment" and what their ultimate goal is - e.g., species protection, combatting global warming, etc. ... but I don't even know where to start looking. All I seem to find are some internet discussions or unsourced gut feelings of well-meaning people. Nothing scientific yet...)

Thanks. Thanks. Thanks for answering (talk) 13:50, 8 July 2019 (UTC)

Please see the work of Professor Bjorn Lomborg You can youtube some of his talks which can be as short as 20 minutes wherre he will cover this topic. Anton 81.131.40.58 (talk) 14:07, 8 July 2019 (UTC)

yes, there are. Lots, actually.

Economically speaking, environment is just a special case of common good (economics) and externality, fields that attracts tons of researchers. Especially when it comes to the so sexy environment. So we have ecological economics, environmental economics, List of environmental economics journals...

Now, as you pointed out, it all depends on the value you bestow to "the environment". An economist can tell you how much it would cost you to do something that the environment take care of (eg: cost of disposing a dead animal, while a vulture will do it for free), that is, price the service of the environment (and some cost if it changes so that it doesn't provide the service anymore); or, the other way round, how much you will benefit from some change (ex: benefits if the Northwest Passage opened). He also can tell you what can be achieved for a given price (eg: what happens if a carbon tax is levied). But he cannot put a price on the existence of a panorama, a swamp, or an insect specie.

So there is no single most effectively spend money on the environment: this will depends on the value the economist uses.

There are, however, lots of least effectively spend money on the environment. Energiewende in Germany for instance (I don't link to our wikipedia article, absolutely unreliable on such highly politicized subject swarmed by militants).

Gem fr (talk) 15:40, 8 July 2019 (UTC)

Re An economist...cannot put a price on the existence of a panorama, a swamp, or an insect specie. Actually he can, by doing carefully worded surveys that ask how much the respondent is willing to pay to keep the panarama etc., and then extrapolating to the whole population and to future generations as well. But of course it's very difficult to elicit responses that are accurate. Loraof (talk) 13:14, 10 July 2019 (UTC)

Looks like to a public worker joke: How do you know if a bridge is to be build over a river? You count the number of people actually swimming across in a year, and multiply by a reasonable estimate of toll and lifetime of the bridge. If the result is more than the cost of building, you do. Gem fr (talk) 17:22, 10 July 2019 (UTC)

Well, you could look at ferry crossings, and what people pay there, but you'd also need to look at people using nearby bridges who would switch to the new one, and perhaps people who opted not to cross the river who would if a local bridge existed. SinisterLefty (talk) 21:31, 10 July 2019 (UTC)

In the case of the swamp, the value is likely negative to those who live there. That is, they are a NIMBY issue. "Lush wetland habitats" sound nice, unless you have to smell swamp gas and battle mosquitoes every day. And finding your dog missing and his leash hanging out of the mouth of an alligator doesn't make locals love swamps much, either. SinisterLefty (talk) 15:33, 10 July 2019 (UTC)

Evidence are that legislations are enacted, and guards paid, so that swamps keep ruining the property, health and life of those living near them, however... So somehow people (most of them NOT living near a swamp, for sure) are very eager to pay for this result. Gem fr (talk) 17:22, 10 July 2019 (UTC)

Coastal swamps do provide environmental benefits, like limiting hurricane damage, so the best solution there is to just ban people from moving there, or, if already there, to provide economic incentives for them to move inland. SinisterLefty (talk) 21:34, 10 July 2019 (UTC)

One thing to be aware of is greenwashing. Spending money on things like "clean coal", for example. SinisterLefty (talk) 03:09, 9 July 2019 (UTC)

I was just thinking I should have mentioned greenwashing (which includes basically ALL that is fashionable and costly, such like renewable energy -- wind, solar --, electric vehicles, recycling, switching back from plastic bottle to glass, etc. Real green is cheap, because it needs as few material, and as few transformation of the material, as possible. Of course all that is cheap is not green; but nothing expensive is). Good that you did Gem fr (talk) 06:40, 9 July 2019 (UTC)

Thanks, but I think most of the items you listed do make sense, at least in some cases. Solar and wind power, for example, make sense where sunlight and wind are strong and consistent, and other sources of power are expensive, such as isolated locations. Electric vehicles could make sense where air pollution is unbearable, like some cities in China. Recycling of lead-acid car batteries makes sense. Glass bottles make sense if you clean and reuse them, like I do.

But, yes, there is a lot of greenwashing, too. Looking at electric vehicles, for example, we have to consider the entire life cycle of the vehicle and batteries, not just "tailpipe emissions". And if electricity in your area comes from burning coal, that's not an improvement over gasoline. I'm also worried that old electric vehicles maybe be junked just because the batteries are weak and replacing them would cost more than the vehicle is worth. SinisterLefty (talk) 07:40, 9 July 2019 (UTC)

Right. Instead of "green", we should talk about "greener". Indeed, in a few case solar and wind are cheaper and greener than, say, coal, but in most case they are not (still; they will eventually, I think), but anyway they never are green. Nothing really is. Gem fr (talk) 10:01, 9 July 2019 (UTC)

To be more specific, my (2 cents worth) understanding of the recommendation are that ... you should just read pigovian tax/pigovian subsidies (and related links) that basically sum up all the issues on the matter Gem fr (talk) 11:23, 9 July 2019 (UTC)

a groups of scientists (?!) was annually (?!) asked how to best spend a considerable amount of money – It sounds like you're thinking of the Copenhagen Consensus. Adrian J. Hunter^{(talk•contribs)} 12:00, 9 July 2019 (UTC)

Thanks for all the input!! Yes, interesting how economics play in. And yes, it seems I (mis)remembered the Copenhagen Consensus.
At the same time, I'm still not much closer to an answer: After all, I'm not a politician or millionaire (neither can I enact taxes nor do I have the money for huge research programs or arming ships for marine cloud whitening), so if I just wanted to donate some modest amount of money, I'd still be no closer to knowing where to donate to actually have a good impact on "the" environment. Whether it's about climate change, about having poison-free habitats, about species preservation or whatever - is there really no reasonable comparison as to where money actually matters more? Any ideas where to start looking for scientifically / economically sound answers? --Thanks for answering (talk) 20:56, 11 July 2019 (UTC)

Kudos to you for actually putting thought into how to maximise donation effectiveness. Picking the right charity can radically change how far every dollar goes, and the world would be a vastly better place if everyone did that. It's a pity that GiveWell and the broader Effective altruism movement tend to consider environmental charities as out-of-scope. I don't have a great answer for you, but this article, though a few years old, may be of interest. Adrian J. Hunter^{(talk•contribs)} 01:36, 13 July 2019 (UTC)

Scop.

Hello,

I have encountered an abbreviation in Wikipedia for which I cannot locate any definition. I am nearly positive that it must be something basic that everyone knows that I don't! I am referring to a listing for Scientific nomenclature. Please see this entry, https://en.wikipedia.org/wiki/Coryloideae. In the first sentence on the second line you will see, "...extant genera - Corylus L., Ostryopsis Decne., Carpinus L., and Ostrya Scop." What on earth does "Scop." mean? It is not the species. It is not the sub-genus, I don't think. It is a bad abbreviation for "subclade," if that is what it is! I've searched Wikipedia and the general web. Help, please. Thank you. Bjb2466 (talk) 15:16, 8 July 2019 (UTC)

Apparently, it's an abbreviation of Scopoli; see here. Dbfirs 15:26, 8 July 2019 (UTC)

Just as, in the same passage, "L." is an abbreviation of (Carolus) Linnaeus, the Latin form of the surname of Karl Linné, and "Decne." is a similar abbreviation of (the Latin form of?) Joseph Decaisne's surname. In the fullest form of Binomial nomenclature, the name (or a recognised abbreviation thereof) is added to show who first scientifically named and described the species in question. "Scop." indicates Giovanni Antonio Scopoli aka Johannes Antonius Scopolius. {The poster formerly known as 87.81.230.195} 2.122.177.55 (talk) 15:46, 8 July 2019 (UTC)

Is there a Wikipedia article that tells us this stuff? If so, I couldn't find it, and there's nothing useful at Scop.--Shantavira|^{feed me} 08:12, 9 July 2019 (UTC)

Author citation (botany). Mikenorton (talk) 08:48, 9 July 2019 (UTC)

Scop (disambiguation) fixed Gem fr (talk) 09:45, 9 July 2019 (UTC)

Thanks. It's actually all at List of botanists by author abbreviation (It would be a major task to disambiguate all of them. There are a lot!)--Shantavira|^{feed me} 10:14, 9 July 2019 (UTC)

There's also List of authors of names published under the ICZN, which includes all (hopefully) of the above plus biologists. {The poster formerly known as 87.81.230.195} 2.122.177.55 (talk) 17:42, 9 July 2019 (UTC)

I think this task is just impossible. But so was the writing of wikipedia, after all. So, step by step...Gem fr (talk) 10:23, 9 July 2019 (UTC)

July 9

Shear force v Reaction (physics)

• Are shear force and Reaction force the same thing??
• Is hydrostatic pressure a term used to describe the tension force in the water? Do we use hydrostatic pressure when we talk about the tension force of water?

--Exert yourself (talk) 13:29, 9 July 2019 (UTC)

!) No. The reaction to a shear force would be a deformation or fracture.

2) Tension ? No. More like compression force. If you are talking about surface tension, that's unrelated. SinisterLefty (talk) 13:49, 9 July 2019 (UTC)

• • Oh! Thank you so much! I feel I can better distinguish between those. --Exert yourself (talk) 03:33, 10 July 2019 (UTC)

Octonion basis vectors

First, I am relatively new to contributing to wikipedia; so I am not sure if I a going about this correctly, or in the correct location to post.

I was reading the page on Octonions, trying to understand some basics before I take on introdution academic texts. In the definition section it made reference to "non-scalar basis elements". I was not familiar with the phrase or the intent, so I did a google search and found about 50 instances of the phrase. None were clear as to meaning, generally they were used in advanced technical papers on various mathematical topics besides octonions. I then came up with zero hits when combined with "definition". I spent about four hours chasing this.

Going outside wikipedia searching on octonions, I realized the concept being described was just the set of basis unit vectors without the scalar unit vector value "e0" a/k/a/ "1". Just for clarification, I should note that each unit basis vector can be multiplied by a scalar value; so when working with an octonion one has nine numbers that qualify as "scalar".

For clarification I edited the octonion page by adding {{e_{1},e_{2},e_{3},e_{4},e_{5},e_{6},e_{7}}.

The phrase "non-scalar basis elements" is correct, just a little knotty for a newbie. It would also be correct to say "the set of unit basis elements when squared equal negative one".

I just got a message on my watch list saying what I had done was rejected because it was "not constructive", and that I should use sandbox. What I have done is parsimonious and most explicit, and nothing else one could write could be more explicit in describing the matter at hand.

If written explicitly, it would have saved me or someone else, from the loss of time. I am not seeking to have the description "non-scalar basis elements" removed, or adding another knotty explanation included.

Not being an expert on the subject, a newbie must check, double check, and keep checking until competent to prove the concept. In hindsight I would have preferred to have flagged the phrase explaining the confusion, and let someone else improve it.

Not sure how to proceed, or if I should ignore and let it go.

'MatthewDougherty (talk) 19:41, 9 July 2019 (UTC)'

Your edit to octonion still stands (at present), and has not been reverted as "not constructive". The same appears to be true for all your other edits. Perhaps you saw the "not constructive" message on a page history, or on another users contributions list, and mistakenly took it as applying to yourself. So thank you for you contributions and please be bold and continue to edit. catslash (talk) 23:36, 9 July 2019 (UTC)

Must have been a timing issue. I originally saw "not constructive", but when writing this post I went back to the rejection to copy something, and found the rejection missing. Not understanding the mechanics of wikipedia editing, I completed my post and pushed the publish changes on this talk page. Since then, I found the talk section on Octonions, so in future I will restrict these topic specific questions to those talk pages. thx, will keep trying. 'MatthewDougherty (talk) 23:59, 9 July 2019 (UTC)'

Yes, Talk:Octonion is the right place to raise any issues regarding the octonian page - and as there are 111 people watching the page, you are likely to get a response. For pages with fewer watchers, it may be necessary to bring the issue here to get any attention - though this is not the intended function of the reference desk pages. catslash (talk) 00:29, 10 July 2019 (UTC)

July 10

High Frequency Distortion Effect

Does anyone know the name of the strange effect that is observed when I play extremely high notes on a musical synthesizer? Basically, when I play an extremely high note, I get an unusually low frequency distortion noise. Also, when I use the pitch bend wheel, the normal effect is to create a simple change in pitch. However, when I do this with extremely high frequency notes, I get a rather unusual effect, which I can only describe as being similar to the rather cliched "radio tuning" sound effect, that is to say the noise you often hear in cartoons and the like when a radio is being tuned. This effect contains some surprisingly low frequencies, and has a sort of "wob-wob" sound to it.

What is the name of this effect, and why does it happen? I have searched the internet and could not find an answer for this question. do any of you know what it might be?

Could somebody please answer this question. The effect I'm looking for has been bugging me for ages now. It is known to effect frequencies of over 10,000 Hz, with frequencies of over 16,000 Hz being particular prominent in this regard. Please can I have an answer as soon as possible!? Thank you. Pablothepenguin (talk) 23:37, 10 July 2019 (UTC)

---Moved from ent ref desk:

Does anyone know the name of the strange effect that is observed when I play extremely high notes on a musical synthesizer? Basically, when I play an extremely high note, I get an unusually low frequency distortion noise. Also, when I use the pitch bend wheel, the normal effect is to create a simple change in pitch. However, when I do this with extremely high frequency notes, I get a rather unusual effect, which I can only describe as being similar to the rather cliched "radio tuning" sound effect, that is to say the noise you often hear in cartoons and the like when a radio is being tuned. This effect contains some surprisingly low frequencies, and has a sort of "wob-wob" sound to it.

What is the name of this effect, and why does it happen? I have searched the internet and could not find an answer for this question. do any of you know what it might be? 92.19.204.231 (talk) 13:13, 9 July 2019 (UTC).

Could somebody please answer this question. The effect I'm looking for has been bugging me for ages now. It is known to effect frequencies of over 10,000 Hz, with frequencies of over 16,000 Hz being particular prominent in this regard. Please can I have an answer as soon as possible!? Thank you. 92.19.204.231 (talk) 13:01, 10 July 2019 (UTC)

I believe its a form of harmonic distortion/resonance, but can't find appropriate references. Try over at WP:Reference desk/Science, perhaps(?) 2606:A000:1126:28D:84CB:D08E:899F:D254 (talk) 16:30, 10 July 2019 (UTC) — Preceding unsigned comment added by Baseball Bugs (talk • contribs)

One possibility along that line is that what is perceived as a single high frequency note is actually a low note and the high note (and perhaps many in between). According to our article on harmonics: "Most acoustic instruments emit complex tones containing many individual partials (component simple tones or sinusoidal waves), but the untrained human ear typically does not perceive those partials as separate phenomena. Rather, a musical note is perceived as one sound, the quality or timbre of that sound being a result of the relative strengths of the individual partials." So, the synthesizer may be using the same method, only the low frequency notes cause resonance, and are therefore magnified to the point where they are audible and also cause distortion. Although distortion may not be the whole story, as I imagine there's a loose connection and that the low frequency causes it vibrate into and out of contact, making the "tuning the radio" sounds. That's my theory, at any rate. If my theory is right, you may be able to find a loose connection and solder it down or otherwise fix the problem.SinisterLefty (talk) 00:53, 11 July 2019 (UTC)

Assuming that your synthesizer is digital, it could be aliasing. catslash (talk) 00:34, 11 July 2019 (UTC)

• String resonance.--TMCk (talk) 09:50, 11 July 2019 (UTC)

I can indeed confirm that a digital synthesiser was being used. Pablothepenguin (talk) 10:54, 11 July 2019 (UTC)

I have been able to create a file demonstrating this effect. It is called . I trust you will know what effect I'm talking about now, then. Pablothepenguin (talk) 11:25, 11 July 2019 (UTC)

OK, that's a continuously changing frequency, like a slide whistle. All I can say is that the synthesizer is malfunctioning. SinisterLefty (talk) 14:24, 11 July 2019 (UTC)

I can assure you, the synthesizer is functioning correctly, it is a virtual synthesizer, so it doesn't have any actual cables. Also, sorry for using this IP Address repeatedly, I sometimes have to edit from a different device that I don't have my account on. 92.19.204.231 (talk) 17:01, 11 July 2019 (UTC), also known as pablothepenguin.

It may be otherwise functioning properly, but this sure doesn't sound like what it should do. SinisterLefty (talk) 20:34, 11 July 2019 (UTC)

Moiré phase resonance -- as demonstrated here: https: // youtu.be/Ql3nMG4EDrI ←[remove spaces] —107.15.157.44 (talk) 21:00, 11 July 2019 (UTC)

Could somebody please explain this effect to me in layman's terms? I would like to know what causes it and why only extremely high frequencies are affected. 92.19.204.231 (talk) 21:35, 11 July 2019 (UTC)

Actually, I don't think that video is quite right, my phenomenon concerns extremely high frequencies of over 10,000hz. Also, my phenomenon sounds a little bit like a dentist's drill. 92.19.204.231 (talk) 22:04, 11 July 2019 (UTC)

A visual analogy?

That effect in the video is done intentionally, of course. Tinkering with the knobs would presumably give a better example of your problem. In your situation, somehow two signals generate interferrence; I suspect the 2nd signal is a harmonic of the primary -- and the phase relationship has become unstable ... or something like that. This creates a waveform somewhat analogous to the animation shown in the Moiré pattern article (see right). Imagine that the stripes in the pattern represent the high frequency crests/troughs in a waveform, and the resulting pattern represents the "wob-wob" effect. Sorta? —107.15.157.44 (talk) 22:48, 11 July 2019 (UTC)

See Beat (acoustics). 173.228.123.207 (talk) 07:56, 12 July 2019 (UTC)

I am rather pleased to report that I have just ran some experiments and tests on Audacity. It would appear from my analysis that the effect in question is mostly do with a concept called Aliasing. This leads to the above mentioned Moiré effect. During my tests, I experimented with a quantity known as the sample rate. The way sample rate works is simple: the sample rate is simply the number of samples per second of audio. An audio programme such as Audacity takes audio level readings many times a second, and records the amplitude at each sample. This information is used to reconstruct the audio for digital playback.

My first experiments concerned pure sine waves. These are just pure frequencies with only the fundamental frequency and no additional harmonics. The sine waves were generated at 10,000 Hz and other nearby frequencies. I first played a 10,000 Hz sine wave together with a 10,100 Hz wave and notes the low beating effect, which produced a 200 Hz resultant frequency. Beating, of course, occurs when two similar but not quite the same frequencies are played together. The frequencies continually move in and out of phase, and selectively develop strong and weak points as a result. The strong points occur when the waves are in phase, and the weak points occur when the waves are offset by 180 degrees or pi radians. Usually with lower frequencies, the beating can be heard as a rather pronounced "wob-wob" effect. This effect is quite common, and can be heard with chorus effects and out of tune instruments. If the frequencies are high enough, or have an unusually high difference between them, then the beating get to a high frequency to have a definite pitch, as with the example above. I also created a sweep which played over 5 seconds, and went from 8,000 Hz to 12,000 Hz. This gave a reasonable pure sound.

I then proceeded to experiment with Sawtooth waves, which contain a very large number of harmonics. I repeated the experiments from above, and noted that the sawtooth wave sweep, again from 8,000 Hz to 12,000 Hz over 5 seconds, contained the effect that I asked about above. I repeated these experiments with sample rates of 44,100 Hz, 32,000 Hz and 384,000 Hz. I noted that the highest frequency you can generate for a particular sample rate is equal to half of that sample rate. I also noted that the weird effect was much less pronounced with the 384,000 Hz sample rate. Finally, I noted that the weird effect had a particular resonance at exact fractions of the sample rate frequency. 92.19.204.231 (talk) 15:00, 12 July 2019 (UTC)

July 11

Another cats question.

Okay I already know that mother cats are known to take care of kittens not of their own, including infants of other species. So what if you have 2 female cats, 1 neutered and 1 non-neutered. And they were childhood friends. Then the non-neutered cat gives birth. Say we shortly take the mother away, then will the neutered female cat attempt to look out for the kittens? Obviously she can't milk, but she could at least look out for them in the event of outsiders. 67.175.224.138 (talk) 04:28, 11 July 2019 (UTC). Edit: I wonder if something like this has ever been experimented. 67.175.224.138 (talk) 04:33, 11 July 2019 (UTC).

Even male cats have been observed to spontaneously start caring for random kittens they just met. At least one wild lioness has been observed taking care of juvenile gazelles. I don't know that anyone has attempted a study that could predict this behavior. Someguy1221 (talk) 04:37, 11 July 2019 (UTC)

Cross-fostering might be helpful. Klbrain (talk) 06:50, 11 July 2019 (UTC)

Had this happen with my own cats. So, yes. --Khajidha (talk) 09:30, 11 July 2019 (UTC)

Would your cat as much bring food to the kittens? 67.175.224.138 (talk) 17:27, 11 July 2019 (UTC).

Being hit by speed of light velocities.

How painful/destructive is it if you were hit by an electron near the speed of light? Then for proton, and cesium atom (the largest non-radioactive atom), and for a water molecule? I heard that if you had something the size of a basketball, made out of nickel, if launched against the Earth can destroy it if it was near the speed of light. Shrugs. 67.175.224.138 (talk) 04:32, 11 July 2019 (UTC).

This question has been answered (more or less) for a baseball, here. --69.159.11.113 (talk) 05:18, 11 July 2019 (UTC)

A single atom or molecule would not do any significant damage; it would just pass through you and back out, just like cosmic rays do. A baseball or basketball is much bigger than that scale. Incidentally, caesium is the largest atom, even without the "non-radioactive" qualifier: francium is smaller than caesium due to relativistic effects. Double sharp (talk) 07:53, 11 July 2019 (UTC)

I don't believe they would behave like cosmic rays, since an atom has an electron shell that would interact with other atoms it passed through. It might still not be noticed, though, as even if it destroys a million atoms, that's still a minute portion of the human body. However, note that actually going the speed of light would be impossible, requiring an infinite amount of energy, so we would have to be content with 99% or so. Also, the person would have to be in a vacuum, or the atmosphere would react with the fast atom. And being in a vacuum certainly would affect the body. Maybe you could have a narrow tube, only a few atoms inner diameter, with a vacuum in it, touching the skin, and fire the atom down that. SinisterLefty (talk) 14:17, 11 July 2019 (UTC)

What would the atom reacting with the atmosphere do? Imo, couldn't an atom travel so fast that it loses it's electrons? 67.175.224.138 (talk) 17:29, 11 July 2019 (UTC).

Or it might never have had them. An Alpha particle is effectively the nucleus of a Helium atom that was created (as a separate entity) without any electrons. {The poster formerly known as 87.18.230.195} 2.122.177.55 (talk) 17:51, 11 July 2019 (UTC)

Right, but the OP specified atoms and molecules, which includes the electron cloud, so I tried to find a scenario where those could hit a person while going nearly the speed of light. Speed alone shouldn't shake loose electrons, but hitting something at those speeds sure could. SinisterLefty (talk) 20:29, 11 July 2019 (UTC)

Something important to understand here is that anything with mass can never reach c (the speed of light in a vacuum), but it can get arbitrarily close. However, the amount of energy needed to accelerate said thing grows exponentially as you get closer to c. See Lorentz factor for more detail. If you could accelerate something to an outrageously high Lorentz factor, you could get its kinetic energy to exceed the binding energy of Earth. To see this, you could try out some calculations yourself using the math from the Lorentz factor article. However, a practical means of doing this is left as an exercise for the reader. You might find this page interesting. --47.146.63.87 (talk) 08:38, 12 July 2019 (UTC)

The relativistic kill vehicle is a trope of science fiction. There are some calculations at the linked article. I think there was once a Wikipedia article or section about the concept, but I wasn't able to find it just now. 173.228.123.207 (talk) 21:49, 12 July 2019 (UTC)

Guys, I purposely said "near the speed of light." And I purposely didn't say a specific percentage like 99% or 95% the speed of light. Please and I'm sick of these posts about "it's impossible to go to the speed of the light" posts. I know that. That wasn't my question. 67.175.224.138 (talk) 03:56, 13 July 2019 (UTC).

Autism question

Is there a name for this strange phenomenon I've noticed in myself? What I've noticed is that when I try to do what I want to do, my body often does something different. Of course, I'm aware that the brain and the rest of the body work together to accomplish things, and the prefrontal cortex does not act in a vacuum. For example, a person might not want to vomit (That choice would involve the prefrontal cortex, right?), but the vomit area of the brain becomes activated and he or she does vomit anyway. However, I've noticed some exceptionally strange things about myself and about how the different parts of my brain try to work together to do things. For example, I might try to walk as straight as I can, and the more I try to walk straight, the more I can't. This also happens when I type. It's as though I don't want to type a wrong letter (such as an "a" instead of an "s"), and somehow, my brain gets confused and makes me type the "a." Now, I realize that autism (especially classical autism - and I have no reason to suspect that I have anything other than that) is known to affect pretty much every single region of the brain, so I'm wondering whether autism somehow affects the "cooperation" between the different parts of the brain. I've heard of conditions such as alien hand syndrome, so I'm wondering if there might be a name for this autistic trait.75.117.54.5 (talk) 06:55, 11 July 2019 (UTC)

Wikipedia does not give medical advice. Bazza (talk) 08:15, 11 July 2019 (UTC)

vomiting is full of info.

normal, not autistic person also experience the "the more I try the less I succeed" effect. A classical example of that is military cadence marching. Or, indeed, typing. This happens when you try to control things instead of letting them happen on their own Gem fr (talk) 01:02, 12 July 2019 (UTC)

I've heard that is called the centipede's dilemma. 173.228.123.207 (talk) 21:37, 12 July 2019 (UTC)

Yes, thank you! I wish I knew that before Gem fr (talk) 10:33, 13 July 2019 (UTC)

Life vest vs Parachute

Why do airlines offer customers a life vest under their seats in the case of a sea "landing". Statistics prove that the chances of surviving a sea landing in a commercial airliner are pretty slim. However, statistic also show that parachuting from high altitude has a fairy low mortality rate (I know, I know, these are trained people taking great risks and carefully calculating their actions etc). I am aware that parachuting at high speed is deeply dangerous and more than likely will kill you, but surely if you're going to die anyway, at least give the customer's a fighting chance to land gently in the ocean to be eaten by sharks rather than smashing into the ocean still strapped to your chair by a useless seat belt. Why a seat belt, air supply and life vest rather than an oxygen canister and a parachute? Thanks — Preceding unsigned comment added by 81.131.40.58 (talk) 10:11, 11 July 2019 (UTC)

If you stop and think about it, your idea is not practical. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:37, 11 July 2019 (UTC)

Much of it is just trying to keep the passengers calm so that they don't make the situation worse. The chances of survival may be low, but they'll be lower still if panicking passengers are running loose and possibly getting in the way of the pilot. --Khajidha (talk) 11:20, 11 July 2019 (UTC)

At the very least, everyone would have to wear their parachute for the entire trip, and the safety card would have to explain how they work... which would get real interesting for someone carrying an infant. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:57, 11 July 2019 (UTC)

Googling "why don't planes carry parachutes" will give you lots of pages with good reasons. E.g. this one. AndrewWTaylor (talk) 13:29, 11 July 2019 (UTC)

Just a few reasons:

1. Parachutes are far more expensive.
2. They are more difficult to put on and use (there are some that automatically deploy, but those are even more expensive).
3. They take up more room and are heavier.
4. They would require opening a door in flight to jump, and almost all passenger planes are designed to prevent that, as the air pressure differential holds the doors shut. DB Cooper was flying in a plane which was an exception.
5. Jumps would need to occur at low altitude and speeds to be survivable. A jet plane likely couldn't get enough lift at those speeds to stay aloft long enough for everyone to jump. SinisterLefty (talk) 14:00, 11 July 2019 (UTC)

Skydiving is usually done from a plane that's flying level. A plane nose-diving toward the ground would make it more difficult. And even forgetting that - as you suggest, the time window of survivability would be rather short. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:33, 11 July 2019 (UTC)

What about fighter jets that have ejection seats, surely this is the same principle and it works for them. — Preceding unsigned comment added by 81.131.40.58 (talk) 14:41, 11 July 2019 (UTC)

Those are highly trained professionals with expensive and sophisticated equipment. Not at all the same as random travellers on a passenger jet. --Khajidha (talk) 14:44, 11 July 2019 (UTC)

PS - Read the article that AndrewWTaylor linked to. Parachuting from a passenger jet at cruising altitude is not just grabbing some rinky-dink canvas bag and strapping it to your shoulders like a book bag. --Khajidha (talk) 14:46, 11 July 2019 (UTC)

Or just convert every seat in the plane to an ejection seat. That shouldn't cost too much. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:09, 11 July 2019 (UTC)

I hope that was meant sarcastically. Among other things, consider that the passenger seating occupies the widest part of an airliner, with lots of other stuff both above and below the passenger cabin. --69.159.11.113 (talk) 20:05, 11 July 2019 (UTC)

Precisely. And yet another reason why the OP's idea is not practical. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:43, 11 July 2019 (UTC)

• In addition to all the reasons given above, consider the time needed to make everyone jump. My guesstimate would be one hour to evacuate a full commercial airplane of a couple hundred passengers (skydiving companies like this say about 10s between jumpers, but that's for people who paid for it, watched the instruction video and are ready, not frightened civilians). One hour might be a tad too much for a crisis situation of "OMG we are gonna crash soon". Even if it is not, it means the passengers are scattered over a very large distance (airplanes go at Mach 0.85 which is about 1000km/h) so the rescue operation is going to be difficult (presumably, the aim of parachuting passengers is not to let them freeze to death in ocean water). Tigraan^{Click here to contact me} 14:58, 11 July 2019 (UTC)

To really understand the motivation, you have to comprehend that the purpose of a life-vest or a life-raft is to improve the statistical rate of survival after a water landing. In that specific type of emergency, many - or all - occupants of the aircraft will live without injury; and they only need to stay afloat long enough for a rescue craft to arrive. These flotation aids are intended to reduce the rate of death by drowning.

The life-vest or life-raft is not designed to be the solution to other types of emergencies.

So, with this context in mind, the line of inquiry would be - why is this specific type of emergency worth preparing for?

To answer that, maybe the best place to start reading is the summary statistics for aviation accidents in the United States. Very few accidents on air-carrier ("airline") operations are actually fatal; very few have any relation to an impact or a mechanical failure. In the event that an aircraft loses partial or total propulsion over land, it is very likely that a pilot can bring the aircraft in for a safe and "normal" emergency landing with zero fatalities.

In the event that an aircraft loses propulsion over water, the water landing is almost certainly survivable; the accident can remain "non-fatal" as long as every passenger can egress and stay floating. So, at a policy level, we're engineering a solution to take a big chunk out of the "pie-chart" of all possible fatal accidents. We're not even trying to solve every accident with this specific method. We have other methods, tools, equipments, policies, and so on, to deal with the other pie-slices. On inspection of the overall "pie" - the set of statistics of all civil aviation accidents, over time - well, the slice of accident-conditions that could possibly be "improved" using a parachute is so small as to be not even worth dealing with. This is a data-driven conclusion based on real research - we solve the safety problems that actually need to be solved, not the ones that people imagine to be serious.

If you're a super-wonk who is actually serious about safety, FAA's Civil Aerospace Medical Institute program in Oklahoma offers zero cost water egress training to interested participants:

• CAMI Safety Training brochure
• facilities brochure.

You can live through a water-emergency, and with training, equipment, and engineering, we can improve the survival rate for more people in more serious emergencies.

If you're looking for more background reading, here is:

• the SAE's standardization body for Aerospace, Committee S-9: Cabin Safety Provisions Committee. They are a team of international engineering experts whose recommendations are codified and recommended by American government regulators (among others).
• SAE Aerospace Standard AS-1354: Individual Inflatable Life Preserver
• 14 CFR §121.340, the specific American legal regulation that mandates a method of emergency flotation for overwater flights, with additional citations to the legislative actions of the early 1960s that led to creating that specific rule. No equivalent legal requirement exists for the provision of parachutes to passengers. Elsewhere in the world (one hopes) the local government has a similar or equivalent standard requirement.

Nimur (talk) 17:01, 11 July 2019 (UTC)

It's even possible that parachutes for everyone could increase fatalities, by increasing the plane weight, such that when it has very limited lift, for whatever reason, this added weight could cause it to crash before it reaches a runway. SinisterLefty (talk) 21:00, 11 July 2019 (UTC)

Not only possible, rather sure. I skydived. Hundred of jumps. And I used airlines, too, so I wondered. Well, after thought, I have rather stay fastened to my seat in crash position. Far better survival chance than pretending to stay cold-blooded, try to wear a parachute with oxygen mask on, then crawl to an exit (in a jerking, rocking and rolling plane full of panicked bodies, luggages, objects, scary sounds...), just to find out that the plane is actually too low (most trouble occurs when landing or taking off, that is, at rather low altitude, while you ask a least 300 m (1000 feet) even in automatic parachuting) for the parachute to do any good (even if I actually put it correctly, which is not sure, and nobody will have checked it for me as we always do before jumping from a stable plane). And, then again, I know how to jump (when everything is OK! I am no super hero and wont claim to do thing properly -- or even just do thing, actually, instead of freezing or panicking -- in a imminent crash context). Untrained people? They might as well go hang themselves; better result.

The only way parachutes could be useful, would be to design seats so that are actually escape pods, quite like in military aircraft. Except that, chance really are that a military aircraft get downed, while civil planes are actually safer than cars, so the point of this is not sure. Gem fr (talk) 23:28, 11 July 2019 (UTC)

I rather suspect that the most likely impact of issuing parachutes to passengers would be to scare them away from flying altogether. As you suggest, plane crashes are rare. Automobile accidents are a much likelier cause of death for a given individual. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:47, 11 July 2019 (UTC)

I concur. Transportation is choke full of example where trying to improve safety has the opposite effect (because it push people away from an already safe behavior, toward a more dangerous one) Gem fr (talk) 00:49, 12 July 2019 (UTC)

The original question is a cousin to the old semi-joking question, Why don't they make the whole plane out of the material they make the voice and data recorders from? The answer is that the plane would be too heavy to take flight. Basically you'd have a big bus with wings. (At least there'd be no need for parachutes.) ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:40, 12 July 2019 (UTC)

LOL. No need for wings either. BTW my understanding is that they seriously consider getting rid of recorders, in favor of immediate transmission (which could allow detecting malfunction and helping in rescue before a crash even happen, instead of just analyzing it. Gem fr (talk) 13:02, 12 July 2019 (UTC)

They should do both. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:17, 12 July 2019 (UTC)

Agreed. Not sure how reliable a transmitted signal is, as it requires more functional equipment than a flight recorder (more power, a working antenna, etc.) and a lack of interference. Also, the signal may be lost if in a mountain valley, or too low over the ocean, etc., that is, the type of conditions that often precede a crash. SinisterLefty (talk) 13:37, 13 July 2019 (UTC)

"Global heating"

How plausible is this scenario? Global heating: London to have climate similar to Barcelona by 2050, Cities of the future: visualizing climate change to inspire action

If that's true, then future really doesn't bode well for the city I'm living in, Zagreb. But, while summers seem to be getting a little warmer on average - I can't really say much for sure from experience, I'm only about 30 - our all time high record is almost 70 years old. I think we would've broken it by now if summers are going to heat up by 7.3C? Also the 7.3C summer temp increase doesn't fit the page's idea that climate will be similar to Louisville, if that really happened we'd be getting in the Port Hedland neighborhood ... 93.136.99.57 (talk) 22:00, 11 July 2019 (UTC)

Note that global climate change does not result in uniform warming. Some areas warm faster, some slower, and some even cool down due to shifting weather patterns. So, you certainly can't expect the same change in Zagreb as in London. SinisterLefty (talk) 23:57, 11 July 2019 (UTC)

grauniad-grade. As they themselves admit, this is "to inspire action". That is, to suspend thinking by fear and sense of emergency. Confidence trick.

London is under the influence of North Atlantic Ocean. Barcelona, under the influence of Mediterranean sea. North Ocean temperature increased at the whopping rate of ... well, it actually cooled. Never mind.

Too bad, this for sure would have been quite an improvement for London.

As a rule of thumb, the closer to the pole you get, the more climate change has effect. Arctic ice is still there, despite it was supposed to disappear long ago it you were to trust the guardian.

As another rule of thumb, the guardian is a cool horror stories collection, full of flamethrowing, cosmos-destroying, undercover nazis detected by ″experts″; but to be trusted, not so much... Gem fr (talk) 00:24, 12 July 2019 (UTC)

The Guardian is not the top resource when it comes to science (nor is any mainstream newspaper btw). Regardless, anthropogenic global warming is real, and so is arctic sea ice decline. Tigraan^{Click here to contact me} 08:39, 12 July 2019 (UTC)

Indeed. But very far from the guardian's rocky horror picture show, which, by its own admittance, is just meant to inspire action by exaggeration aka plain lies (also, my understanding of motivation is that this is very counter-productive, BTW. "stop, you fools, your action will result in Troy in flame" only results in the demise of the warning people). Newspapers (any of them) being "not the top resource when it comes to {whatever}" is quite an understatement Gem fr (talk) 09:29, 12 July 2019 (UTC)

• For our non-British readers, the Guardian is a well respected quality newspaper, particularly known for its investigative journalism. I suspect Gem fr has ideological reasons for their very inaccurate description of it, or perhaps they meant to talk about the Daily Mail, in which case the statement was largely accurate. Fgf10 (talk) 08:53, 12 July 2019 (UTC)

to call the guardian a "well respected quality newspaper" is a grauniad-grade joke. I suspect Fgf10 has ideological reasons for their very inaccurate description of it, contradicted by example I just gave and countless "OMG thing are far worse that they were/expected to be" clickbait articles. I concur that the daily mail is another cool horror stories collection, but at least the DM as the good taste (hum hum) to mitigate and cheer up readers with lots of boobs and royals/celebrity futilities, while the guardian I see boringly humorlessly serious-minded. Gem fr (talk) 09:29, 12 July 2019 (UTC)

You might not like it, but those are just the facts. It is only not well respected in far-right circles. Also, you do realise the don't make up the science right, they just report on it? You seem to understand both the science behind climate change and how journalism works. -- Fgf10

You might like it, but calling this kind of garbage "facts" or "science" is just outrageous. And the word you should use instead of "report" is "stage". I'll change my mind the day the guardian publish a piece like "remember the "scientist" who told you that arctic ice would disappear in 4 years? well, 7 years later, turns out his "science" was astrology-grade". Spoiler-alert: not gonna happen. (as for your name calling It is only not well respected in far-right circles, the shame is on you) Gem fr (talk) 12:36, 12 July 2019 (UTC)

Please see the works of Bjorn Lomborg much of the climate change drama is exaggerated. It is real and it is a problem but we will cope. As for the UK being hotter than Barcelona by 2050, A. Barcelona will also be heating up according to mainstream climate change theories, or will be underwater and B. UK hotter than Barcelona? Sounds great, bring it on! and C. evey one please try to remain calm and remember the Y2K crisis which everyone conveniently forgot on January 2nd 2000 after realising they had been duped. My 486 still worked just fine. Anton 81.131.40.58 (talk) 10:33, 12 July 2019 (UTC)

Y2K was not a hoax. My company had a lot of date fields that were specifically written in YY-MM-DD format which had to be reconfigured to YYYY-MM-DD in order to prevent the year going to 00 and causing trouble with date comparisons. Your PC's date calculation algorithm may not have had that problem. And if it was "forgotten" after the year rolled over - well, that was the entire point of doing that work. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:33, 12 July 2019 (UTC)

Bjorn Lomborg is an economist and quite shaky on the science. And his main concern was about the relative importance of climate change compared to things like malaria and I would have to agree that allocating resources for everything is a big problem. But we have to do something about climate change and the sooner the less painful. As to Y2K there was no organized Y2K denial and the reason it passed without trouble was because people did take it seriously in advance. Dmcq (talk) 11:24, 12 July 2019 (UTC)

Actually, it turns out that "the sooner we do something about climate change, the less painful" became "we must show we care, and greenwash as much as possible, even if what we do actually worsen the problem we claim to solve" and "what a great opportunity, almost as good as terrorism, to frighten people into 1984-like politics" and "screw the western working class, we have a cosmos to save (and Chinese work force to tap for even more profits, what a coincidence)". And this resulted in silly move such like Energiewende in Germany, subsidizing Tesla cars, the destruction of ironworks with only effect to move the industry to India or China, and solar/wind crap. Renewable energy is making giant step progress, and will take over at some point, but it was a child prematurely put to work. At some point you have to evaluate things not out of their aim, but out of their actual results. Gem fr (talk) 12:36, 12 July 2019 (UTC)

• Sorry no offense, but it sounds to me that you don't believe in climate change at all. I'm interested in the opinions of people who do agree with the scientists, on whether we can expect the change to suddenly turn catastrophic in the next 30 years. (Since summer warming here has been so far on a pace far far slower than 7.3C per 30 years.) 93.136.69.75 (talk) 21:15, 12 July 2019 (UTC) (OP)

Au contraire, climate change is real. Hell, humanity works hard just for this very purpose. Some say we may even skip the next glacial period, which would be great for those alive at the time (not me, not you, so we would be mad if we cared anyway). Gem fr (talk) 10:00, 13 July 2019 (UTC)

The thing is, your question has no scientific sense at all. Can you spontaneously turn into a lump of gold? Yes you can, according to well established quantum mechanics theory; chances are low, though... can we expect the change to suddenly turn catastrophic in the next 30 years? has a very simple answer, as science goes: NOBODY-KNOWS, Period. Longer (same) answer: Science (math of chaos) is very clear, this just cannot be answered with any serious level of confidence. And in fact, if you read them carefully, all such scaremongering pieces are written in a special way. Choke full of if and could and may and trust me I am the expert (which actually translate as my work is guarantied science-free according to Feynman "Science is the belief in the ignorance of experts", but unaware minds don't know that) and I am not telling you that, you just figure it yourself, you are so smart. So that, afterward, the author can deny having made any prediction, so he wasn't wrong. Not even wrong. So, just disregard it. Even "is there anything fun to watch?" would be more important than falling prey to unwarranted worries (and there ARE more important questions, right now). Gem fr (talk) 10:00, 13 July 2019 (UTC)

I've moved your answer here because it has nothing to do with the question I asked 47.146, and I'd like to have an answer to that question, I think it would tell me immediately how trustworthy. Please reply here if you will. To reply: are you aware that all those things you describe can be applied to your own writings? You're asking me to assume that a large amount of papers on climatology are the result of malevolent confidence trickery and fraud, while your own statements are vague and unfalsifiable. For example "screw the western working class, we have a cosmos to save (and Chinese work force to tap for even more profits, what a coincidence)", do you expect me to believe that climate change activism caused job automatization on the whole or are you going to correct me that you meant to say that it was actually a tiny contributor? Your own logic is only backed by your own reputation as a person well-read enough to write "Grauniad", and some things you write ("Science (math of chaos) is very clear, this just cannot be answered with any serious level of confidence.") conflict with disciplines of science that have been around for decades (at least catastrophe theory and climate tipping points). I want this paper to be wrong too but what you write convinces me no more than that paper, so please back off with the attacking what-a-stupid-thing-to-ask tone. 93.142.75.226 (talk) 22:41, 13 July 2019 (UTC) (OP)

You want me to substantiate, fair enough.

Did climate change activism caused job automatization? No. It, for instance, caused the USA to hinder its coal industry, and it caused the EU to subsidize destruction of ironworks in Europe and its moving to India, and it caused the ~trillion euros, paid through electricity price ~2x what it is in France, hurting most low income homes. This qualify as "screw the western working class etc.", don't you agree? (It also probably hindered, not caused, job automatization and efforts to cope with global pollution).

Indeed, math conflict with some part of climatology. Not all climatology, for obvious reasons, among which: Edward Norton Lorenz. Hell, "we cannot say at present, on the basis of observations alone, that a greenhouse-gas-induced global warming has already set in, nor can we say that it has not already set in" (ref name="Lorenz91" https://www.sciencedirect.com/science/article/pii/B9780444883513500350 ), and The Guardian push a paper that says he can calculate how much the greenhouse-gas-induced global warming will be in a specific city? (although, as noted before, "will" is not used, only "could" and conditional and innuendo)? The same newspaper that pushed a paper telling that the arctic ice should had disappeared years ago, and never pointed out that it never happened? What a joke, although, not a funny one. That 9-year old kids are scared to put vinegar on baking soda for fear of global warming is not funny (see question below), it is child abuse and terrorism.

You want this paper to be wrong? I don't. I want it to be able to be wrong, to begin with, so it could qualify as science. But can it be? Is there is a way you can disprove it? Can you put a fact in front of it and say "see? this happened (resp: not happened), that your paper said id could not happen (resp: had to happen), so your paper is wrong"? Answer is: no. It is, literally, not even wrong. Not science. Just discard it, as if it never happened as far as science is concerned (it did happen, of course, but in the propaganda universe aiming to -- and succeeding in-- scare 9-years old).

sorry you are upset, but, nevertheless, your question has no scientific sense at all -- which doesn't make it stupid-thing-to-ask at all, either. It is just another instance of "my horoscope says I have great love opportunity today, is it true?": we can answer that astrology is garbage, but we have no way to scientifically assess whether someone do have great love opportunity or not. Gem fr (talk) 09:18, 14 July 2019 (UTC)

19 years and you still can't admit your folly huh Bugs? tsk tsk Anton 81.131.40.58 (talk) 14:18, 12 July 2019 (UTC)

It had to be done. To have not done it would have been the folly. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:16, 12 July 2019 (UTC)

For once, I agree with Mr Bugs. That no catastrophe such as a plane falling out of the sky actually occurred, does not tell us anything about whether or not it would have happened had the Y2K bug not been fixed. The point was, it was seen by serious, reasonable, practical people as a distinct possibility. That the community took steps to make sure that no such event occurred is a testament to the thoroughness with which this issue was addressed. There was no element of folly in this. It's a bit like getting your kids vaccinated; they might never have got the disease anyway, but you're making sure they don't. That they don't get it doesn't prove it was folly to vaccinate them in the first place. Unless you're an anti-vaxxer, in which case I have nothing more to say to you. -- Jack of Oz ^{[pleasantries]} 00:58, 15 July 2019 (UTC)

As an additional comment, I've seen models that indicate that one of the areas that will be least affected by the planetary increase in temperature in terms of local temperature is the US East Coast (Boston to North Carolina or so) since any melting in Greenland is likely to feed more cold water into the cold current going south along the US East Coast... — Preceding unsigned comment added by Naraht (talk • contribs) 16:58, 12 July 2019 (UTC)

Bad as this may look, it's just a minor prelude to much worse to come. As pointed out here: "The history of the Earth system is a story of change. Some changes are gradual and benign, but others, especially those associated with catastrophic mass extinction, are relatively abrupt and destructive. What sets one group apart from the other? Here, I hypothesize that perturbations of Earth’s carbon cycle lead to mass extinction if they exceed either a critical rate at long time scales or a critical size at short time scales. By analyzing 31 carbon isotopic events during the past 542 million years, I identify the critical rate with a limit imposed by mass conservation. Identification of the crossover time scale separating fast from slow events then yields the critical size. The modern critical size for the marine carbon cycle is roughly similar to the mass of carbon that human activities will likely have added to the oceans by the year 2100."

And we can read here: "As discussed earlier, parallels exist between the Anthropocene and the PETM in terms of carbon input and climate change. Does this also imply similar impacts in terms of species extinction and recovery? We argue that the Anthropocene will more likely resemble the End-Permian and End-Cretaceous catastrophes, rather than the PETM. First, the present extinction rate of the Anthropocene is more than 100 species per million species per year, while the fossil record indicates background extinction rates of marine life and mammals of 0.1–1 and 0.2–0.5 species per million species per year, respectively [93]. In other words, the current rate of species extinction is already 100–1000 times higher than would be considered natural. The causes for the current extinctions are diverse, including factors such as changes in land use and fresh water, pollution, exploitation of natural resources, etc. Second, with respect to ocean acidification and impacts on marine calcifiers, the anthropogenic carbon input rate is most probably greater than during the PETM, causing a more severe decline in ocean pH and saturation state (figure 5). In addition, changes in ocean chemistry and sea surface temperature will be imposed on ecosystems that are already affected by other environmental factors. Analysis of the marine fossil record suggests that, if the Anthropocene mass extinction rivals the K-T or End-Permian disasters, recovery will take tens of millions of years [16]. At this point, there are obviously large uncertainties regarding the progression of the rate of extinction and origination, dispersal and success of species in the future. However, if the current trend of species extinction continues, the geological record tells us that humans will have a major and long-lasting impact on the evolution of species on this planet for millions of years to come." Count Iblis (talk) 19:45, 12 July 2019 (UTC)

It took me some time to grok this. What does the "critical size for the marine carbon cycle" stand for? I'm guessing it's the point where evaporation of CO2 from oceans causing heating and heating causing evaporation of CO2 will create a runaway reaction. Could this really produce warming on the scale of several degrees per decade? I'm aware that most likely Earth is toast long term (thank you old people), I'm wondering if it's plausible that the climate will completely change within my lifetime. 93.136.69.75 (talk) 22:26, 12 July 2019 (UTC)

The paper Count Iblis discussed focuses on what might be sufficient to provoke a mass extinction. It isn't directly looking at global temperatures. As to your original question, the site predicts for Zagreb an increase in the maximum summer high temperature by 7.3 °C. The average temperature (the arithmetic mean) is predicted to increase by 2.3 °C. These are two very different figures, and well within the ranges predicted by models for much of the globe. If you haven't, read, if possible, The Uninhabitable Earth (I suggest the annotated version). In the past, even more rapid changes in climate have happened; during the Paleocene–Eocene Thermal Maximum, average global temperatures rose by around 5 °C within about thirteen years. Now, will this happen in our near future? Not necessarily. Predictions from the IPCC Fifth Assessment Report are based on different Representative Concentration Pathways, which predict between 0.3 to 4.8 °C of warming depending on emissions. (We're already above the low-end estimate.) Again, these are average global temperatures. To predict the effects on a specific region, you need studies that look at that region. For one example, models for Tibet give a high-end estimate of 6.1 °C. Note that for human habitability, humidity is as important as air temperature. Wet-bulb temperature takes into account both; heat index is another such figure. And of course, the effects of global warming go far beyond air temperature, and will affect weather patterns, agriculture, sea level, human health, flora and fauna, and much more. --47.146.63.87 (talk) 00:48, 13 July 2019 (UTC)

Yes, the average summer temperature increase seems reasonable. In the past decade avg temperature in summer months was 3C over the 1960-1990 mean, so another 2.3C over another 30 years is about at pace (avg temperature for the entire year has been growing slower). What is this maximum temperature tho? The average highest temperature of the year is now I think probably 35-38C, I'm having a hard time seeing how we can push another 7C on top of that with our humidity levels, let alone that that would be the "best case scenario", and how that would put us near Louisville and not for example, Dubai. 93.136.69.75 (talk) 03:01, 13 July 2019 (UTC) (OP)

Phase diagram

Can a compound's phase diagram be determined based purely on theoretical analysis of the compound's structure, etc., or must it be found observationally? Loraof (talk) 23:48, 11 July 2019 (UTC)

In theory, yes. In practice, oof. This is related to what are called equations of state. That is, functions of the state of matter (temperature, pressure, etc) that yield physical properties of that matter (density, phase, etc). Since atoms and molecules are just obeying ordinary quantum mechanical principles, you could in theory simulate any system and use the simulation to derive approximate equations of state, or you could attempt to derive an analytical model (essentially, no simulation, just "math out" an equation from first principles). People try this. It's hard. Realistic systems are too complicated, generally, to either accurately simulate or derive anything completely analytically. So approximations are made. That is, the imagined system is simplified. If you do a Google Scholar search for "primitive model of water" you will find many papers on attempts to derive usually portions of the phase diagram, but it's about more than just water/ice/vapor - the goal is to know all of the physical properties in a given condition. Someguy1221 (talk) 00:10, 12 July 2019 (UTC)

To focus on one area that gets particularly wierd, the materials where the solid/liquid line points up and to the left, which are the materials where the solid floats in the liquid (ice, Plutonium, Bismuth, Germanium, Gallium, and Silicon (but apparently not antimony). I've never seen any sort of calculations which group all of these materials together, and if there are, I doubt the reasons for ice and Plutonium are quite the same.Naraht (talk) 16:55, 12 July 2019 (UTC)

July 12

Use for transplants of Human equivalent of Nerves used to move ears in other animals?

I'm trying to remember a piece of trivia that I was once told. It was that for transplants to fix areas where nerves had been damaged that a source of the same body transplants were nerves on the side of the head that in other animals like cats are used to move the ears. Humans have the nerves, they just don't do anything. Is this (or something close to it) correct?Naraht (talk) 12:07, 12 July 2019 (UTC)

thanks to your question I just discovered that Nerve transplant is actually a thing Gem fr (talk) 12:47, 12 July 2019 (UTC)

The nerve concerned may be the Auricular branch of vagus nerve that supplies the Posterior auricular muscle responsible for the ancient vestigial (in humans) pinna orienting reflex. DroneB (talk) 00:53, 13 July 2019 (UTC)

July 13

planet with size Mars can not impact with earth

It said that any mars sized planet impacted earth to form moon. my calculations show it is impossible .--Akbarmohammadzade (talk) 04:01, 13 July 2019 (UTC)

Giant Impact Hypothesis- the planet Theia — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 04:03, 13 July 2019 (UTC)

(here to learn, not answer questions) Did you take into account the fact that the solar system wasn't settled yet, then? Usedtobecool ^✉️ ✨ 06:35, 13 July 2019 (UTC)

Have you read Giant-impact hypothesis? What do you think is impossible - that such an impact could have occurred, or that Earth would have survived the impact, or that the moon could have resulted from the impact and found a stable orbit?-gadfium 06:50, 13 July 2019 (UTC)

How about you show us your calculations. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:10, 13 July 2019 (UTC)

NO! I mean, if the calculations were validated and published in some (real) physical review, at some point it will show in wikipedia. But Ref Desk is not place to discuss such hard science Gem fr (talk) 08:16, 13 July 2019 (UTC)

The OP has stated a premise. It is totally reasonable to ask what the basis of that premise is. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:22, 13 July 2019 (UTC)

why we suppose that it impacted when in such case two planets only start to form couple planet system? in fact when it was nearing the earth , new planet get the earth out of its orbital , and for the reason of gravity field effect , two planets only were been rotating each other.--Akbarmohammadzade (talk) 10:06, 13 July 2019 (UTC) we see Pluto and Charon do so--Akbarmohammadzade (talk) 10:07, 13 July 2019 (UTC)

WP:NOR Gem fr (talk) 10:37, 13 July 2019 (UTC)

The two would need to be headed on a collision course, not a near miss. This seems extremely unlikely today, but there were a lot more such objects flying around the solar system in the early days (all the craters on the Moon, where they are preserved, are a fair indication of that), and over billions of years most of them either hit the Sun or planets, were ejected from the solar system, or found a stable orbit. SinisterLefty (talk) 13:25, 13 July 2019 (UTC)

It's a little late to submit papers, but the Ames lunar summer science summit is in a few days (registration open through July 18!) and this year is sure to be a big one - commemorating fifty orbits since the return of Apollo 11! :Anyway, without being a little too blunt, I'm inclined to quote my own words from a couple of months ago responding to amateur research here on Wikipedia's science reference desk. "Until you have established credibility in these fields by following well-established career-trajectories working toward the professional level, the experts don't really care what opinions you have about their work. You are free to critique advanced physics - or to complain that you don't understand it - but it will be about as productive as if you complain about the coaching strategy for a professional sports team. Your opinion carries no weight, and your critiques don't merit attention, because you aren't playing in the same league."

So for example, when Apollo 17 astronaut-scientist publishes an outside-the-mainstream opinion on planetary impact, like the famous Moon’s Origin And Evolution: Alternatives and Implications,... we take note of his idea, even if we don't accept every single detail; but we look at it because he's worth listening to and has previously established his credentials; but when random Wikipedia contributors do the same, we sort of hold them to a different bar. It's not necessarily the case that scientists disagree with your independent research: it's more the case that scientists don't care enough about your work to actually bother looking at your calculations. It is a harsh and competitive world, and if you haven't proven your mettle by conducting well-respected peer-reviewed research before the time you finish formal university years, well... then, the scientific-community-at-large is too busy studying the work that other bright people have done on these interesting topics.

Nimur (talk) 18:11, 13 July 2019 (UTC)

There are examples of amateurs making respected contributions to science. Astronomy, Chemistry, and Archaeology are fields that come to mind. See, for example, “Amateurs and professionals in chemistry: The case of the periodic system” You need to do your research, and if you ask politely and present your work concisely, some experts will look at your work. After that the road to wider recognition is to get published in a peer-reviewed journal. You do not necessarily need to be an expert in the field to achieve this. The good thing about being an amateur is that amateurs will sometimes bring a different perspective to matters. The not so good thing is that you need to do a lot more homework to be able to speak the language of whatever the applicable field is. Sandbh (talk) 00:03, 14 July 2019 (UTC)

Producing CO2 from vinegar and baking soda

At a science fair I saw a"baking soda and (colored) vinegar volcano". Was nice.

There was an argument how much CO2 is emitted (starting with a 9 years old that was worried it will contribute to global warming :) )

So my question is as follow: How much (in grams) baking soda and how much (in liters) 5% vinegar produce 1 cubic meter of CO2 under 1 atmosphere pressure? אילן שמעוני (talk) 18:00, 13 July 2019 (UTC)

• First you need Avogadro's law and the ideal gas law to do some thermodynamics.

From these, one mole of CO₂ will occupy 24.5 litres at room temperature the (molar volume). i.e. Your "one cubic metre" will need $1000/24.5{mol}$ of CO₂ (that's about 40 moles of it, which gives many experienced chemists a quick idea of if they're talking about beakers or tank trucks of it)

The next bit is chemistry.

To make a mole of CO₂ you need at least enough of each ingredient. You could use a stoichiometric mixture, but usually one is in excess (and doesn't react, because it's run out of the other reactant).

Baking soda is sodium bicarbonate, NaHCO₃

Vinegar is acetic acid, CH₃COOH (5% by volume, here)

Their reaction is NaHCO₃ + CH₃COOH → NaC₂H₃O₂ + H₂O + CO₂

This isn't quite the full detail of the reaction,[1] but it's OK to show us the end result. What it means is that we need one molecule of baking soda to react with one molecule of vinegar, to give us one molecule of CO₂. To make our cubic metre of gas, we need $1000/24.5{\text{ mol}}$ of each. As liquids and solids are more dense than gases, that's a lot less than a cubic metre of those! But how much?

A molecule of baking soda (NaHCO₃) has a molar mass of 84.0066 g mol⁻¹ (I cheated and looked that up from WP). I could work it out too, by adding up the individal atomic masses for each of the four elements in it (and counting three times for all those oxygens). That's $23+1+12+3\times 16=84$ (real chemists will object to my approximations here)

Acetic acid is 60.052 g·mol⁻¹

So we'll need at least $84\times 1000/24.5{\text{ g}}\approx 3.5{\text{ kg}}$ of baking soda. The vinegar will need 2.45 kg of acetic acid, or about 2.33 litres of it. But as this is 5% vinegar, that's 47 litres of vinegar.

So overall, to make a cubic metre of CO₂ gas from one of these volcanoes, that's a couple of sugar bags of baking soda, mixed with a dustbin of vinegar. Quite a bit for a science fair project! But maybe, you could catch the gas bubbles produced and measure them?

Andy Dingley (talk) 18:31, 13 July 2019 (UTC)

Thank you! Not only an answer, but detailed walkthrough! אילן שמעוני (talk) 19:09, 13 July 2019 (UTC)

While it certainly is such a trivial amount that it can be ignored, kids sometimes don't grasp relative scales. So, you might suggest they plant a tree to make up for it. Even a tiny tree ought to do it. SinisterLefty (talk) 20:00, 13 July 2019 (UTC)

"Wood is composed of up to 50 per cent carbon". [2] 1 m³ of CO2 weighs about 2 kg (depending on temperature), [3] so your tree would need to grow to 4 kg to offset. Alansplodge (talk) 21:58, 13 July 2019 (UTC)

It's also a fine opportunity to distinguish between capturing, and sequestering: if you plant a tree and it transforms carbon dioxide from the air back into a solid form of plant matter, by way of photosynthesis... well, what happens to those atoms of carbon after the tree dies, rots, and evolves into a new form? In the short term - perhaps just a few years - that organic matter will rot and oxidize the carbon, meaning that each atom of carbon will probably evolve back into carbon dioxide molecules, and be re-released into the atmosphere.

On the other hand, if we bury the dead tree, and provide specific conditions, ... it has the potential to evolve into coal, and (perhaps) later into e.g. natural gas and other fossil-carbon. This may take a very long time... but as long as it stays underground, those atoms of carbon are not floating through our atmosphere.

And then, if some future civilization digs that coal out of the ground and burns it to power a heat-engine for a new millenium, they may re-release those very same atoms back into the air...

What we really want is to take those atoms of carbon and put them inside some long-term biotic process that converts them into an almost-geological substance that won't be evolving back into atmospheric carbon dioxide...

Nimur (talk) 22:54, 13 July 2019 (UTC)

Even if 100% of the carbon goes back into the atmosphere in a few decades, that would help slow global climate change, allowing us time to come up with other solutions, or at least move our houses off the coasts. SinisterLefty (talk) 01:07, 14 July 2019 (UTC)

Do you have a house on the coast? My family do. And I wondered if I needed to care. Answer is no. f*ck the scaremongers. At worse, stilts would be needed, and that's it. Global climate will keep changing anyway, so the question is rather: should we fear that Antarctica turn back to a rain forest, or that the Earth turn into a snowball? Is it good, or bad, that we may help skip next glacial period? I (and you) will be dead by the time those question really matter, anyway, so my answer is: just solve current real issues. Gem fr (talk) 09:44, 14 July 2019 (UTC)

If global warming is inevitable, just relax and enjoy it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:41, 14 July 2019 (UTC)

Yeah, Gem: it's nice that you live somewhere where you can easily put your house on stilts, or build a new one. Are you going to tell us how to do that with dozens of large cities worldwide like London, New York and Delhi. Apres moi, le deluge? {The poster formerly known as 87.81.230.195} 2.122.177.55 (talk) 20:17, 14 July 2019 (UTC)

Actually, I'll never need stilt: this is why I am so angry at those f*cking scaremongers. And you better check your data (and turn angry, too), if you still believe them. People who will need stilt are those who should already use them (in Polders for instance). Ever heard about Raising of Chicago? Scaremongers somehow always fail to mention that

1. movement of the land matters more than change of sea-level.

2. sea-level has been rising for millennia, and concerned places are already dealing with it. A change is barely visible.

3. nobody (almost) cares. If they care, they just need to build, right now, at a proper higher height. (well, actually, I know a few place where they care, because it has been happening for a long time -- climate change having nothing to do with it--). So that, by the time it becomes a problem --this needs decades--, if it even ever comes, it is already solved. but Nooooo... why use simple, cheap solutions, when you can owl The End Is Nigh, let's destroy the civilization, stop giving health care to elderly, etc, to save New York, eh? Gem fr (talk) 21:27, 14 July 2019 (UTC)

Delhi is more than 200 meters above sea level so that's a total brain fart.--TMCk (talk) 21:29, 14 July 2019 (UTC)

And kudos to reasonable Gem which whom I apparently just edit conflicted.--TMCk (talk) 21:34, 14 July 2019 (UTC)

I don't see putting everything on stilts as a cheap and easy solution. How do you do that with skyscrapers ? Best plan I could see is to abandon ground floor (or use it to store junk you don't much care about) and make 2nd floor into new ground floor. Then raise all the roads by one story, too. Still a massive project, but cheaper than rebuilding inland or at same site on stilts. SinisterLefty (talk) 03:16, 15 July 2019 (UTC)

July 14

Is my drawing of the phases of the moon from different latitudes correct?

Phases of the moon at selected latitudes with Mare Crisium highlighted

Hi,

I drew this image based on the diagrams at astronomy.stackexchange.com and commons:Category:Lunar_phases. To make the images match, I had to flip the orientation before full moon. File:Ficha_y_actividad_3.jpg also shows a flip around the full moon.

That doesn't seem quite right. Is it correct? If so, why is it so? Otherwise, how do I fix it?

Thanks,
cmɢʟee⎆τaʟκ 02:22, 14 July 2019 (UTC)

You've got the first quarter and last quarter on a slant. What time of night are you depicting? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:05, 14 July 2019 (UTC)

Well the waxing moon will be more visible after sunset, so assume it is viewed just after sunset, and t waning moon, assume it is viewed just before sunrise. You have the crescents unequal, but at the same time they will appear to be about the same size at the different places around the world. Another point is that if the moon is entirely visible from the South Pole, it is below the horizon at the North Pole. Graeme Bartlett (talk) 08:17, 14 July 2019 (UTC)

Thanks, @Baseball Bugs: and @Graeme Bartlett:. I'd like to depict either midnight or when the moon is highest in the sky. I didn't know that the rotation changes over the night. Lunar_phase doesn't make that clear. Can you briefly explain how the rotation changes over the night?

Good point about not being visible from both poles. The diagrams do not necessarily represent the moon seen at the same time, but how a moon during a particular phase looks like from these places. The images in each column are exactly the same, just rotated to an angle corresponding to the latitude. I just found that the unequal size is a bug in thumbnail rendering; the SVG file shows it as intended. I'll try to fix it. Thanks, cmɢʟee⎆τaʟκ 08:32, 14 July 2019 (UTC)

You have fixed the thumbnail unequal rendering. To get an idea of the moon angle, imagine someone standing at the equator looking at the moonrise, and the moon is in the plane of the equator. Then at the same point in time imagine other observers in a circle around the earth looking at the same moonrise or moonset. If the person is at +X° latitude, the they will be standing at that angle to the person at the equator and the moon will have apparently rotated −X°. At the North Pole it is −90°, and past that in the moonrise side of the Earth the moon will appear at X-180°. The formula should also work if lattitude X is negative in the Southern Hemisphere. Graeme Bartlett (talk) 00:18, 15 July 2019 (UTC)

We've had some of this discussion before. How the full moon looks, for example, will change depending on whether you're facing north or south, regardless of which hemisphere you're in. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:51, 15 July 2019 (UTC)

You have the right idea but it varies by a lot. I can see the waxing crescent horns almost straight up at 40.75n when it's the right part of spring and ecliptic latitude is high. Also it has to be very thin for this to happen due to geometrical reasons and some years get closer than others (assuming you are not traveling to other longitudes of 40.75n to see the youngest moon of the month). If you could see the crescent past the point of naked eye visibility you could even see it the wrong way (the southern hemisphere side of straight up). Sagittarian Milky Way (talk) 01:05, 15 July 2019 (UTC)

The reason it doesn't seem right is because you are drawing it when it is setting or rising, whichever occurs at night and NOT at dusk or dawn, whichever has it above the horizon. Sagittarian Milky Way (talk) 01:10, 15 July 2019 (UTC)

Production of curium-250

I asked this on the talk page at Talk:Curium#So how is curium-250 produced? about a year and a half ago, but never got an answer: so how exactly is this isotope produced? The article notes that its production by neutron absorption in reactors is unlikely because ²⁴⁹Cm is likely to decay before it can absorb another neutron, so only nuclear explosions could create high enough neutron fluxes to make it. While ²⁴⁴Pu has the same problem, it can be produced through the alpha decay of ²⁴⁸Cm. Are these just extracted from what old nuclear explosions made (as the half-lives are long enough that they should still mostly be around)? Double sharp (talk) 07:40, 14 July 2019 (UTC)

"Curium is a byproduct of plutonium production activities and results from the successive capture of neutrons by plutonium and americium, generally in nuclear reactors."[4] Looks like ORNL has a production route.[5] And OSTI reports that thermonuclear explosions are indeed a good source of it.[6] DMacks (talk) 08:10, 14 July 2019 (UTC)

Hot chrome

While living in Arizona in summer with a two-tone car, I noticed the following. The white metal top was much cooler to the touch than the dark (cobalt blue "sea blue") metal part, of course. However, the chrome door handle was much hotter than either painted metal. One would think that chrome, being highly reflective, would be cooler -- but its not; why is that? 2606:A000:1126:28D:E5B5:B088:3A46:1619 (talk) 17:33, 14 July 2019 (UTC)

The sheetmetal of the car is thin steel. The doorhandle is diecast zamak, much thicker. What you may be feeling here is not a temperature difference, but a heat difference. They may both have been at the same temperature, but when you touch the thin sheet, that temperature soon drops as heat is conducted into your hand. With the thicker and heavier casting though, the amount of heat energy stored is far greater, and your hand perceives this: it stays hot, even while you hold it.

An infrared thermometer (quite cheap these days) might reveal more. Andy Dingley (talk) 18:37, 14 July 2019 (UTC)

Thanks, that makes sense. I hadn't considered the thickness aspect -- Thermal mass might also come in play. Unfortunately, I no longer have that car (and modern cars, if they have any chrome at all, have chrome-like plastic). 2606:A000:1126:28D:E5B5:B088:3A46:1619 (talk) 18:58, 14 July 2019 (UTC)

Postscript: Agaaach!, I found one just like mine online; theoretically could be mine from Arizona -- sold for $110k! (albeit fully restored). 2606:A000:1126:28D:E5B5:B088:3A46:1619 (talk) 19:20, 14 July 2019 (UTC)

Another significant difference is the thermal conductivity. The metal will conduct the heat fast into your hand, unlike the cloth/plastic. You can notice the same effect with a blow torch. When it hits a brick, the surface glows red or orange immediately, but on metal it takes much longer to reach red heat.

Also, I don't know if it plays any role here, but "white" objects may or may not also be reflective to infrared and ultraviolet, which could affect the temperature. SinisterLefty (talk) 02:06, 15 July 2019 (UTC)

Yeah, any native Arizonan could tell you that (one can tell a newcomer: if they have a black car). 2606:A000:1126:28D:E5B5:B088:3A46:1619 (talk) 03:24, 15 July 2019 (UTC)

The complement of centrifuging

If you separate a mixture of liquids by applying a centrifuge force to them, how would you call the complement of it, I mean, the force to obtain a homogeneous mixture of liquids? — Preceding unsigned comment added by C est moi anton (talk • contribs) 20:56, 14 July 2019 (UTC)

Homogenization? —2606:A000:1126:28D:E5B5:B088:3A46:1619 (talk) 21:01, 14 July 2019 (UTC)

You can't homogenize a mixture by applying a single force to it. Instead there needs to be some mixing of the fluid, which is done by applying a non-constant (i.e. inhomogeneous!) set of forces to it: some sort of shear force, where part of the mixture goes one way and an adjacent portion goes another. This can be done by turning the mixture over (concrete mixer), stirring it slowly (food mixer), quickly (blender), extremely fast (colloid mill), ultrasonically (homogenizer or sonication) or blowing it through a small nozzle (homogenizing valve). Andy Dingley (talk) 21:29, 14 July 2019 (UTC)

(edit conflict)Mixing (process engineering), Mixing (physics). Also, check emulsion Gem fr (talk) 21:32, 14 July 2019 (UTC)

In labs with a centrifuge you may well find a Shaker nearby; Vortex shakers are particularly fun. Klbrain (talk) 22:19, 14 July 2019 (UTC)

If you find a Quaker nearby, don't bother; they object to all forms of violence, and are not particularly fun. 107.15.157.44 (talk) 22:59, 14 July 2019 (UTC)

Often done to cans of paint. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:57, 14 July 2019 (UTC)