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July 19

Does gravity always point to *somewhere* in the Earth's core?

I know there are points on the Earth's surface where gravity points along a line that detectably misses the Earth's center of mass. But are there any where a line in the direction of gravity doesn't even go through the Earth's core? NeonMerlin 08:11, 19 July 2018 (UTC)

No, the Earth's gravitational field is nearly spherically symmetrical. Deviations from this symmetry are small. Ruslik_Zero 08:45, 19 July 2018 (UTC)

[e/c] :No. Assuming the Earth is a homogeneous density sphere, (which it is not) the gravity vector will always pass through the geocenter. However, since the Earth is actually a bit elipsoidic, (see Reference ellipsoid) there is a difference in angle between spherical and ellipsoid normals (Vertical deflection -- see also: geoid). This difference is very small, however, relative to the diameter of the Earth's core. Also, since the core is more dense than Earth's average, this will add even more "attraction" to the center. There are some gravitational anomalies (local variations of the gravity field) that distort the force vector angle, but doubtfully enough to bypass the core; there might be an artificial condition where this is not true -- perhaps standing right next to Fort Knox? —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 09:05, 19 July 2018 (UTC) ... since your two questions are diametrically opposed (colloquially, not literally), the answers are "yes" and "no".

The core is really big, with a radius of 3,470 km, it would have to be a huge deflection (33°), which is highly unlikely - see vertical deflection, which talks about deflections up to 50 seconds of arc. Mikenorton (talk) 09:30, 19 July 2018 (UTC)

• Guys, that's the kind of question where you need to show the numbers.

Gravity of Earth is the relevant article here. The two most important effects that explain local variations of gravity are (1) the centrifugal force due to Earth's rotation and (2) the fact Earth is not exactly round but slightly flattened at the poles. The article states that the combined effect is a 0.5% change in g between poles and equator (this is why all space rocket launching pads are near the equator). By comparison, local deviations are about 0.005% of g (5e-4 m/s2 max changes, g~10m/s2).

The exact details of how much of the variation in magnitude changes the direction of the gravity vector depending on the latitude need more calculus than I am willing to do, but fortunately very rough assumptions get us what we want. In the worst case scenario, the 0.5% change in g's magnitude comes from an additional pull perpendicular to g (this maximises the deviation). A bit of trigonometry (solve cos(theta)=1/(1 + 0.5%) for theta) tells us the deviation is less than 6° (by the way, this is higher than I would have expected).

On the other hand, Earth's inner core is seen from an angle of two times 10.8° (some more trigo with Earth radius = 6400km, core radius = 1220km). So even with all assumptions lined up in the worse case, we still get that the gravity vector will pass through the inner core. Tigraan^{Click here to contact me} 09:40, 19 July 2018 (UTC)

Indeed. The Schiehallion experiment measured deviations from the local zenith of around 11 seconds of arc. Similar (but less precise) measurements around Chimborazo measured deviations of 8 seconds of arc. Over a distance of 6360 km (radius of the Earth) these sizes of deflections result in a deviation of less than 1 km away from the geometric centre of the Earth. Gandalf61 (talk) 11:43, 19 July 2018 (UTC)

Re "(this is why all space rocket launching pads are near the equator)". The difference in gravitational force is not the main reason rockets are launched from near the equator. Rather, it's because the earth's rotation means the rocket is already traveling east at close to 1000 miles/hour even before it launches. The additional velocity means less fuel required. The hard part of getting into orbit is achieving orbital velocity, not reaching a specific height. [1] [2] — Preceding unsigned comment added by CodeTalker (talk • contribs)

Huh... I somehow thought that was the same effect, but of course it is not (speed in the geocentric frame of reference vs. centrifugal force in the terrestrial, non-inertial frame). Struck accordingly, see also discussion below. Tigraan^{Click here to contact me} 08:06, 20 July 2018 (UTC)

To dispel some very common misconceptions: spacecraft launch sites can be located anywhere on Earth. The geographic location of the launch site is selected for many reasons, not the least of which is orbital dynamics; but there are many other factors, including range safety, redundancy, and convenience - it's important to have easy access to a bunch of rocket scientists, who don't necessarily all want to live on the launch site! Here's a list of NASA's primary launch sites; but not all American orbital (and sub-orbital) launches are managed by NASA. Notably, yesterday a New Shepard 3 launched from West Texas, an operation that was largely conducted without overtly depending on NASA's money or help.

I would use caution before spouting anything about equatorial rotational inertia unless you've worked through the orbital flight dynamics equations - orbits aren't really that simple - and I can spout some counterexamples off the top of my head. For example I've been to spacecraft launch sites at Kodiak Island and Vandenberg Air Force Base: sites from which the spacecrafts can fly westbound or northbound or pretty much where-ever they want to fly. Quoting directly from NASA's website, "Kodiak Island is one of the best locations in the world for polar launch operations, providing a wide launch azimuth and unobstructed downrange flight path..."!

Nimur (talk) 18:33, 19 July 2018 (UTC)

Do they launch low-inclination orbits from Kodiak? Sagittarian Milky Way (talk) 19:51, 19 July 2018 (UTC)

With enough ΔV, you can get to any orbit! That maneuver would be called a "dog leg" on the launch trajectory, and it's expensive (you have to spend fuel to do it) - but any orbit is possible if the people buying the launch want to use their mass (and dollar) budget in that way. Nimur (talk) 22:22, 19 July 2018 (UTC)

Indeed. Likewise a launch from the equator that ends up going over the poles would require a dogleg. Not sure whether it would use more energy than was gained by the equatorial launch -- it feels like it should but I would have to do the math. --Guy Macon (talk) 23:45, 19 July 2018 (UTC)

Orbital inclination changed are ludicrously expensive in terms of energy. If they weren't, there wouldn't be separate low and high inclination launch sites. An extreme example, a LEO craft launched from KSC want to transfer to a 90 degree inclination polar orbit. Plane change delta v for circular orbits is :$\Delta {v_{i}}={2v\,\sin \left({\frac {\Delta {i}}{2}}\right)}$. Assuming a LEO orbital speed of 7 km/s, the delta v required for that plane change is 7.4 km/s again. Or almost as much as it took to launch in the first place. Of course, there are tricks to lower that, but it illustrates my point. Doglegging during launch is severely restricted by overflight considerations on most launch sites. Fgf10 (talk) 07:06, 20 July 2018 (UTC)

Maybe sort of related: shell theorem. Although the Earth isn't perfectly symmetrical, the deviation is pretty tiny given the scale of the Earth. The standard factoid is that the Earth is, to scale, smoother than a billiard ball. --47.146.63.87 (talk) 06:54, 20 July 2018 (UTC)

No. A pool ball is much smoother than the (whole) Earth would be if it were shrunk down to the size of a pool ball, though much of the Earth’s surface is indeed smoother than a pool ball. DroneB (talk) 13:11, 20 July 2018 (UTC)

July 20

Photon as "information"

Sometimes I hear photons described or used synonymously with "information". Can anyone help me understand or point me to resources that explain this comparison?

As an example, in a youtube video on the Black_hole_information_paradox, at around 3:45, the speaker states that, "The black hole radiates particles, mostly photons - that contain no information. Eventually the black hole must completely evaporate into those particles leaving no clue as to what fell into it in the first place."

I understand the evaporation and paradox aspects of what is being said, but am unclear how "information" and "photon" relate. — Preceding unsigned comment added by 128.229.4.2 (talk) 14:56, 20 July 2018 (UTC)

A photon is not information; a photon can be used to carry information, if and only if some property of the photon can be controlled - like when it gets emitted, or what its frequency is, and so on. Formally, that would mean that we can express this "controllable" property using a causal relationship to some other property; then, if we took a measurement of the output property, it would have carried information about the causative property that we did not directly measure.

In the case of an engineered system like fiber-optic communication, individual photons don't actually carry the information: instead, information is encoded into the rate of arrival of groups of photons, treated as an ensemble. The arrival of any one specific individual photon is called shot noise. The arrival of a whole lot of photons within a specific interval, per the engineered specification of the system, carries information.

There is a fun mathematical conundrum of quantum mechanics here - how can one single event be noise, but if we put two otherwise identical events together, they constitute a non-noise signal? This is the property of coherence. In real engineered systems, we use more than two photons so that we can build reliable machinery; but in the realm of theoretical physics or in the study of natural systems, we might investigate the behavior of this single-particle information-carrying behavior using the mathematical and analytical tools of thermodynamics; and we might construct testable hypotheses using the methods of experimental physics; and then we might use those tools to draw conclusions that apply to the more difficult realm of black hole thermodynamics.

Ultimately, when you hear a pop-science publication talking about why black holes do (or do not) emit "information," they are using loose terminology to describe the incoherent emission of radiated energy. Whether those statements are accurate, or valid, depends on the quality and currency of the documentary you're watching!

Nimur (talk) 17:10, 20 July 2018 (UTC)

There is something out there about the concept of physicality of information. I haven't found a layman explanation of it (I tried googling). Apparently somehow information is as "real" and permanent as particles of matter? There are Conservation laws but that article does not contain the word "information". Black hole information paradox kind of hints at it but seems to lack an explanation why it is a paradox. Any help on this for us non-quantum-theorists? Or am I chasing a red herring, in which case can you explain why the black hole information paradox is a paradox? 85.76.73.51 (talk) 17:28, 20 July 2018 (UTC)

The "paradox" is a way to express a disagreement about whether a property's measured state is statistically certain, or absolutely certain. Some physicists believed these words described distinct concepts; and certain specific mathematical models of the black hole provided an example where we could differentiate between the two conditions. As of the time of this writing, the consensus seems to be − there is not any paradox, because there is no actual way to distinguish these two conditions apart. (One of the very last peer-reviewed publications by Stephen Hawking was Information loss in black holes, (2005), in Physical Review - if you can read and understand that paper, you can understand the paradox and Prof. Hawking's position regarding its resolution... and if you can't read and understand that paper... well... you're one of many).

I mean, it's a little bit of a disservice that this "paradox" has been brought to the forefront of the popular conception of modern physics. It's a minor debate about the minutia of the problem. To really understand it, you've got to invest a lot of up-front intellectual effort. And if you actually do that, you'll find many more interesting things to spend your intellectual efforts on! Nimur (talk) 17:41, 20 July 2018 (UTC)

Oh, I don't know Nimur, I find the epistemological questions here, including those involved with that particular question, endlessly fascinating. Anyway, here are the two most accessible/least technical sources I was able to find on the matter for the OP, one of which takes it's title and general thrust from exactly the question the OP has posited in their inquiry: Physical_information, [3]. There's a bevy of additional information out there, though, if you know the right search terms, so if these fail to address your questions, OP, let me know. Snow ^{let's rap} 06:08, 21 July 2018 (UTC)

Thanks Snow, the link to Physical_information was definitely helpful. 128.229.4.2 (talk) 14:29, 23 July 2018 (UTC)

Happy to be of assistance. :) Snow ^{let's rap} 18:32, 23 July 2018 (UTC)

That photons are not information, but carry information is a helpful clarification Nimur. Thank you.

I also came across another video that says "Light not only interacts with matter, it is also altered by it, and can be used to gather information about the world around it, with almost no delay...". This helps me understand. 128.229.4.2 (talk) 19:05, 20 July 2018 (UTC)

There has been quite a bit by Leonard Susskind equating quantum entanglement with wormholes. I am not fit to really recommend the best of it, but there may be a way to get at physicality of information that way (I don't know). Wnt (talk) 21:28, 21 July 2018 (UTC)

Balance and vision

Does the human brain use vision to establish balance? Does a blind or short sighted person have worse balance? Would closing your eyes make you have worse balance? Clover345 (talk) 19:08, 20 July 2018 (UTC)

Yes, vision plays a role. In most people, the semicircular canals are the most important factor, and vision only plays a minor assistive role, along with proprioception. However, people whose semicircular canals are non-functional (this happens in a substantial fraction of deaf people) may have to rely entirely on vision to balance. See our Balance disorder article for more information. Looie496 (talk) 20:02, 20 July 2018 (UTC)

A standard clinical test for vestibular function is to ask someone to stand, then ask them to close their eyes. The loss of visual information, in addition to a loss of vestibular cues, leads to them losing their balance. It needs to be done with someone available to support them as they sway. Klbrain (talk) 22:48, 22 July 2018 (UTC)

How germs get inside the body

I'm using "germs" as a collective term for viruses, parasites, fungi, and bacteria. They can all be called "microorganisms", but that name is a mouthful. So, I'm sticking with "germs" and "bugs". I am aware of the ways that germs get inside the body - by vapor, by food and water, by broken skin, and by intimate touching. What makes the inner lining of sexual body parts so defenseless against pathogens that some pathogens ONLY use this route to climb onto another individual? Perhaps, the vaginal walls, unlike skin, don't have layers and layers of protection. So, germs can easily pass through the cells or infect the cells. Take HIV, for example. There seems to be no reported cases of HIV being able to infect a person through contaminated food. So, HIV cannot survive in food or in the water supply or pollute the air. It can only spread by bodily fluids - using contaminated needles, breastfeeding, and having sexual intercourse. Also, unlike the digestive system, the vagina is not acidic enough to burn the bugs. And some bugs don't travel through air, because they can't. They can only travel by close contact, and sexual intercourse is a super-close contact. The man and woman during coitus are not next to each other. The man's penis is placed into the woman's vagina, and if sperm can travel up to the uterus, then so can bugs and germs, can it? That is literally inside an organ. This question is not about how a bug infects a cell, but how a bug - especially a bug that primarily relies on super-close contact - gets inside the body. SSS (talk) 19:11, 20 July 2018 (UTC)

Mucosa is a useful term here. Very few infectious organisms make it through unbroken skin. The usual routes are inhalation, cuts, the digestive tract (not all of them, as it's a permeable but hostile route) and also (as you copiously mention) sex. There's also an issue of transmission from an infected person - some diseases are hard to catch from someone, because they're not releasing it except by bodily fluids, and then some diseases (such as haemorrhagic fevers) are far more easily transmissible because they produce fluids, or more of them, than are normally present. Ebola is a sexually transmitted disease, but then so's everything. However STDs are those which are only transmissible (in significant numbers) by sex. Andy Dingley (talk) 21:09, 20 July 2018 (UTC)

A key concept here is cornification. Cornification leaves external skin covered by multiple layers of dead cells which are uninfectable and present a physical barrier over the cells that could be infected. Many internal surfaces also have stratified squamous epithelium, but it is not cornified, needs to be kept moist, and doesn't have the same degree of resistance. This is why "mucous membranes" are a target for colds and worse. Now "mucosal immunology" gets much more complicate than this - this paper is about HIV-infected T cells outside the body wandering around epithelium somehow sniffing for the epithelial cells right right over stromal macrophages - these T cells form an "immunological synapse" that delivers the virus to be transcytosed through the epithelial cell into the macrophage to infect it. This is obviously some very specific biology being hacked by the virus; it is almost like a single cell's version of an STD! Wnt (talk) 21:12, 20 July 2018 (UTC)

Upside down glasses

I'm looking for the article about the glasses/experiment where they put those on people to make the whole world upside down. First, they fell about. Then, after a day or so, they got used to it. Then, when they took them off, they fell about again. Do we have coverage of that at Wikipedia? Anna Frodesiak (talk) 20:08, 20 July 2018 (UTC)

See George M. Stratton. Mikenorton (talk) 20:11, 20 July 2018 (UTC)

Thank you, Mikenorton. I think we need a bunch of redirects to it. Anna Frodesiak (talk) 20:14, 20 July 2018 (UTC)

Actually, I just found Neural adaptation#History with similar content. What should be done? Anna Frodesiak (talk) 20:15, 20 July 2018 (UTC)

That image of a "Modern version of inverting mirrors with harness" sure doesn't look very up to date to me. Martinevans123 (talk) 20:47, 20 July 2018 (UTC)

Looks like a skateboard helmet and medical tape. Anna Frodesiak (talk) 20:49, 20 July 2018 (UTC)

Yes, after a trip to A&E on a bad night? Probably even more effective than beer goggles. Martinevans123 (talk) 21:12, 20 July 2018 (UTC)

As a start I've changed "Perceptual adaptation" in the "see also" section of the Stratton article to "Neural adaptation" so at least there is a clear link between the articles. Apart from that, I'm not sure what should be changed as the content is not identical. Mikenorton (talk) 20:31, 20 July 2018 (UTC)

Sounds good. What about redirects? I think these glasses have a different names. Search engines say reversing goggles, prism glasses, and we could make up a couple that we guess visitors would type into the search box, like upside down glasses. Target? Anna Frodesiak (talk) 20:40, 20 July 2018 (UTC)

I can find inverting glasses, inverting spectacles, inversion goggles, inverted vision glasses and upside down glasses as well, so lots of options. As to the target, currently the section in the Stratton article looks like the best bet. Mikenorton (talk) 21:03, 20 July 2018 (UTC)

Okay, created several redirects based on what you wrote above, example here. Many thanks, Mikenorton. Anna Frodesiak (talk) 02:32, 21 July 2018 (UTC)

Rubbing alcohol

If you sterilize your hands with it, can it go into your body and make you dead? Anna Frodesiak (talk) 20:41, 20 July 2018 (UTC)

Rubbing alcohol is typically used for disinfection on skin. SSS (talk) 20:50, 20 July 2018 (UTC)

(edit conflict) WP:NOMEDICAL and all, but that sounds highly unlikely given that it's a common ingredient in many hand sanitizers and our article on it notes that it's "used primarily as a topical antiseptic". Drinking it would be a very bad idea, though. Ian.thomson (talk) 20:52, 20 July 2018 (UTC)

Thank you. That's what I thought. Anna Frodesiak (talk) 20:56, 20 July 2018 (UTC)

(EC) Our article states "Poisoning can occur from ingestion, inhalation, absorption, or consumption of rubbing alcohol", so assuming that you're not intending to drink it and you're not going to eat something with your hands still covered in it, the main thing is probably to use it in a well ventilated area - for absorption, short exposure should be fine " Dermal exposure to the liquid and vapour. There is little absorption through intact skin, but significant delayed absorption over 4 hours postulated (Martinez, 1986). Note risk of inhalation after prolonged skin exposure (sponging, etc.)" from here. Mikenorton (talk) 20:58, 20 July 2018 (UTC)

• Yes. But it's no big deal. We can metabolise a lot of alcohol, no problem. I use a lot of them in my workshop and I'm getting fussier as to which. Alcohols are OK, acetone is OK, I've replaced my hexane with heptane because of the hepatotoxicity risks, and I avoid benzene or carbon disulphide or chlorinated solvents.

I use a lot of methylated spirits, such that I've nearly run out and I'm facing a hard task to replace it. The "standard" stuff is bright purple, stinks of pyridine and is mostly cheap methanol with some ethanol in it. Don't drink it - methanol is bad for you (standard antidote is vodka, as a clean source of ethanol). But if you're a summer woodworker, you really want to avoid both the purple dye and the stench. It's very hard to buy the industrial grade without them though.

If you work in healthcare, the the vast use of alcohol hand sanitisers these days is a problem. They degrease the skin, and skin oils are an emollient to soften the skin and stop it cracking, also to make the skin less permeable. So degreased, cracked, heavily sanitised skin becomes more of a risk for infection. If you're doing this twice every half hour, then it's also important to moisturise. Andy Dingley (talk) 21:20, 20 July 2018 (UTC)

I also highly recommend against gargling with it. It burns much worse than 80 proof ethanol. Sagittarian Milky Way (talk) 23:47, 20 July 2018 (UTC)

Thank you all! Anna Frodesiak (talk) 01:35, 21 July 2018 (UTC)

Andy, is there anything you do not know? :) You must be very handy about the house. So, are you saying hospitals have no use for good ol' rubbing alcohol without the extras? When they give you an injection, what do they use on the little cotton ball? Anna Frodesiak (talk) 01:35, 21 July 2018 (UTC)

There's a difference between what you rub on the patient (once or twice) and what you rub on the staff (fifty times a day). As we've increased the sanitisation of staff so much in recent years, we're now seeing chronic issues that were unexpected - such as the skin degreasing effect. Andy Dingley (talk) 08:53, 21 July 2018 (UTC)

Ah, okay. And yes, →we've gone overboard with this germ killing thing. A bit of Cussons Imperial Leather is fine with me. And nobody gets food poisoning here much. I guess we all get a bit of this and that, so we're immune. I know geckos run on our clean dishes before use. We never got sick. Anna Frodesiak (talk) 08:57, 21 July 2018 (UTC)

There aren't many reptilian diseases which are transmissible to humans. Mice would be quite another matter. Flies are a problem, not because we catch fly diseases, but because of their unclean habits with other human waste. Andy Dingley (talk) 19:07, 21 July 2018 (UTC)

Hi Andy. That's good to hear because Haikou has no mice and very few flies. Anna Frodesiak (talk) 20:21, 21 July 2018 (UTC)

I'm going to call a major on the claim "we've gone overboard with this germ killing thing" in response to the topic of discussion namely hand sanitisation in healthcare settings and especially hospitals. (To be clear, I'm not saying Andy Dingley was making that claim, it seems to originate from Anna Frodesiak.)

It's well recognised that Hospital-acquired infections are a major problem worldwide causing many deaths and other negative consequences. With the increasing prevelance of antiobiotic resistance, colonisation [4] is also a major problem in itself even when it doesn't lead to an infection at the time. (Increasing antibiotic resistance is also one reason why just throwing antibiotics at the problem when it occurs, even ignoring that it doesn't always work even without resistance, is clearly not a solution.) </p

By no means do these all come from staff hands but hand hygeine, staff, patient and visitor is generally considered an important factor in reducing infections and colonisations. Our article albeit unsourced says Handwashing frequently is called the single most important measure to reduce the risks of transmitting skin microorganisms from one person to another or from one site to another on the same patient. This says something similar [5]. More generally, there are many studies demonstrating the benefits of good hand hygeine in reducing HAI including I think colonisation.

About the soap vs. hand sanitiser issue, AFAIK the big factors tend to be time and facilities. Proper hand washing generally takes IIRC 45 seconds or so. Drying then adds more time. I'm not sure how much worse improper handwashing performs, although insufficient drying definitely can definitely be a significant problem [6]. While hand sanitiser misuse likely also negatively affects performance, the main requirement tends to be ensuring it covers the entire surface of both hands and rubbing over the hands until dry [7] so is somewhat easier to follow. Also as AD mentioned, for staff, we're talking about something which is often supposed to be performed every 30 minutes or less, and maybe also after every contact with a patient. For visitors and patients, especially those with limited mobility, the number who will or able to visit a sink to wash and dry their hands compared to those who will use the sanitiser at the bed or door is likely to be fairly different.

At least for my local DHB, and also by that CDC ref to some extent, the general recommendation in healthcare settings is if the hands are visibily soiled e.g. with blood, urine, faecal matter to use soap and water, but otherwise hand sanitiser is sufficient. (I think handwashing is recommended after visiting the toilet without checking for visible soiling.) Regular moisturisation is also recommended (well for the DHB recommendations at least at least). However I don't think using soap instead of hand sanitiser is considered wrong provided proper steps are followed. Actually I wouldn't be surprised if it's better if really done as regularly.Although I'm not sure if bar soap is not going to work well in many healthcare settings. (They may be used for surgical hand scrubs although medicated ones seem to be the minimum recommended [8] [9].) Note that as the CDC ref also says, in many settings outside of healthcare, hand sanitisers are only recommended if water and soap are not available.

I'm not sure why you brought up food poisoning. AFAIK it's often only one, and probably a minor one at that, of the risks of infections in healthcare settings. Note that we should not conflate the problems and solutions in healthcare settings with those in other areas. For example, I'm fairly sure many proponents of the hygiene hypothesis and those who think there is excessive use of antiseptics (which includes the CDC and many other healthcare related organisations) and excessive concern about bacterial counts etc especially in homes who will say this has limited relevance to hygiene requirements in most healthcare settings where there is generally a congregation of patients with infections and patients with weaked immune systems. (And even within healthcare settings there are differences, e.g. surgical handscrubs vs normal hand hygeine.)

That said, while I don't know about the specifics of Haikou, I'm fairly sure food-borne illness are a significant problem in a lot of China as they are in pretty much all of the world with significant numbers of humans. If anyone is claiming otherwise, this isn't just a case but an extraordinary claims require extraordinary evidence case IMO since basically no one else has come even close. (So to be clear, this isn't an anti-China thing, it applies to pretty much everywhere.)

This Lancet world report article (which I presume means it's not peer reviewed) [10] mentions how although the number of reported deaths is very low, it's very likely this is in part because of the limitations in the monitoring systems there and mentions some of the challenges etc. The WHO estimates 125 million people falling ill a year in the Western Pacific region [11]. While they list individual countries at least there, my earlier point remains if the claim is made these are nearly all coming from Japan, Philippines, Viet Nam, South Korea, Malaysia etc [12]. (Actually I think you can exclude Japan, it looks like WPR B itself is around 120 million [13], probably also can be derived from [14] or [15].) Admittedly one of the biggest causes of death, liver cancer from aflatoxin, may not fall under the ordinary definition of food poisoning. And that, and parasites another major problem aren't really affected by hand hygeine. And to be clear again, I don't want this to be some sort of pro or anti China bitch fest. This [16] for example shows that China did very well in terms of meeting the target for the "Mortality rate attributed to exposure to unsafe water, sanitation and hygiene".

Nil Einne (talk) 13:56, 22 July 2018 (UTC)

NIST and WTC's dust

Is NIST conducted a research of WTC's dust as part of NIST's investigation of the collapse of WTC 1, 2 and 7? 37.142.4.56 (talk) 21:25, 20 July 2018 (UTC)

Wikipedia has a fairly extensive, well-referenced, and decently written article on this topic at Health effects arising from the September 11 attacks. You can use that as a starting point for your research. --Jayron32 21:29, 20 July 2018 (UTC)

Carcinogens often take several decades to cause cancer so you couldn't know the full effects now or even in 2030. Asbestos use tailed off very long ago and people contracted asbestosis from before then for quite a long time after. It'd be interesting to see if the 2031 cancer getting rate is higher for people who lived in Downtown Manhattan and Brooklyn then similar places like Midtown and Queens. I often looked to see which way the Ground Zero smoke string was pointing and never saw it get very far from the climatological average direction (westerlies). Minutes or hours after the collapses, the visible ash string stretched to the horizon or almost (Ground Zero is only 16 acres remember), it was at least c. 10 miles long for days and took weeks before you could only see smoke from less than 10 kilometers away from a low roof. If you stood on a street pointing to the heart of Ground Zero in mid-December you could still see smoke from smoldering underground fires from at least hundreds of yards away. Sagittarian Milky Way (talk) 23:45, 20 July 2018 (UTC)

So It's a yes or no? 37.142.4.56 (talk) 06:26, 21 July 2018 (UTC)

The objectives of the NIST investigation are listed here and the final reports themselves are linked here. I don't know the answer to your question, but with enough reading you could find it.--Wikimedes (talk) 07:11, 21 July 2018 (UTC)

July 21

Giving birth

In movie scenes in which the mother is giving birth, a person may say, “Push!” to order the mother to push the baby out. Is the mother really pushing the baby out the same way feces is pushed out the digestive tract? Can the baby go out by itself? SSS (talk) 01:07, 21 July 2018 (UTC)

Here is a book you might find at a local library or bookstore: How Sex Works (1994), which has chapters on pregnancy and childbirth. The book gives an informative, objective overview in a manner that is suitable for citation as an encyclopedic reference. Wikipedia also has a detailed article on childbirth, from which you can find links to related articles on anatomy and physiology. Nimur (talk) 02:06, 21 July 2018 (UTC)

This site by physical therapists describes some of the exercises used, and comments that doing "perineal bulges" "trains you to push during delivery without holding your breath. Holding your breath while pushing is call Valsalva. Valsalva can decrease the rate of blood flow back to the heart, lower maternal blood pressure, decrease maternal blood oxygen and blood flow to the placenta, and increase the risk for injury. It also can increase fetal head compression and fetal distress." From that description it sounds like the Valsalva maneuver, also known as a tactic for defecation, is not recommended for delivery but is used. However, bear in mind that the colon and uterus each have their own set of powerful muscles, which are of course distinct. Wnt (talk) 11:33, 21 July 2018 (UTC)

Can the baby go out by itself? No, the baby has a decreased level of consciousness during delivery. (I swear I read this somewhere, but for the life of me I can't find any source right now. Help would be appreciated.) In a "normal" birth, the baby is pushed out by the muscles of the uterus. If this doesn't go right for whatever reason, you have obstructed labor, and medical intervention may be necessary. --47.146.63.87 (talk) 07:39, 22 July 2018 (UTC)

The uterus is made of smooth muscle which can contract independently of any voluntary control, and it doesn't even need an intact nervous system in order to do so. Therefore, contractions can continue while someone is unconscious, and sometimes this (rarely) has led to vaginal delivery while unconscious. Usually medical/nursing staff wouldn't let this happen, preferring the more controlled caesarian. Klbrain (talk) 23:23, 22 July 2018 (UTC)

The mother doesn't even need to be alive... coffin birth --TammyMoet (talk) 10:49, 23 July 2018 (UTC)

If an expectant mother is killed in an accident medical staff are often able to save the unborn child. 86.133.26.146 (talk) 10:56, 23 July 2018 (UTC)

July 22

Light on the Explorer 1 rocket

Explorer 1

On the rocket that launched Explorer 1 you can see a light on the rocket just before it turns from the cylindrical part to the conical part. What is the reason for this light? Bubba73 ^{You talkin' to me?} 02:01, 22 July 2018 (UTC)

WAG tracking the spin rate without telemetry. Also presumably a rocket needs nav lights.Greglocock (talk) 07:43, 22 July 2018 (UTC)

A spacecraft may have navigation lights, but I doubt if they'd be required or useful on ascent stages, which are kinda obvious when they're burning and aren't usually around for very long afterwards. That said, Explorer 1's fourth stage remained attached to the payload, but who would have been able to see a navigation light on it? {The poster formerly known as 87.81.230.195} 2.219.34.253 (talk) 08:34, 22 July 2018 (UTC)

It may be so they could see spin or something, which may be why it was launched at night (another WAG). The light is near the top of the first stage. Bubba73 ^{You talkin' to me?} 18:59, 22 July 2018 (UTC)

By 'need' I meant legally obliged, not that they were necessary for function. Greglocock (talk) 20:01, 22 July 2018 (UTC)

If I was a rocket designer, I'd definitely look for oppprtunities to include things that didn't interfere but look cool. This is not the main reason why I'm not a rocket designer. --Dweller (talk) Become old fashioned! 10:37, 27 July 2018 (UTC)

July 23

How much water is needed to block various species from reaching an island they would've thrived on if there was a landbridge?

Thus if you find them on the isle they were either introduced or came when there was less water.

How much is needed to allow an average population of at least 0.0000001 but much less than if there was a landbridge? (i.e. pedigree collapse or they can't find each other from too low of a mobility to population density ratio)

This is often prevailing wind and/or current dependent right? Wind and current going towards the island would lengthen this distance. Sagittarian Milky Way (talk) 21:05, 23 July 2018 (UTC)

Some birds can cover 1000's of km of ocean without landing. But there are other birds that don't like to go more than 10m from tree to tree. Over time humans have developed means to colonise land further away, so I suspect that now 20000 km of sea would not stop a human colonisation. But 100,000 km may be too much! Graeme Bartlett (talk) 00:07, 24 July 2018 (UTC)

This is a topic with connections to why Australia has marsupials (kangaroos, koalas, etc) and most of the rest of the world has placental mammals, and there is very little overlap. The standard explanation is the existence of the Wallace Line between Bali and Lombok in Indonesia. It's currently 35 kilometres (22 miles) wide and very deep, but would have been narrower during various ice ages. It has existed for a very long time. The Wallace Line article addresses the question fairly directly, stating "many birds do not cross even the shortest stretches of open ocean water". HiLo48 (talk) 00:19, 24 July 2018 (UTC)

Aren't birds and especially flying insects sometimes blown where they don't want to go by storms? Also I've heard that in Polynesia land birds aren't normally found more than 20 miles from land, or out of sight or something like that. Sagittarian Milky Way (talk) 02:00, 24 July 2018 (UTC)

It would be difficult to give a meaningful figure, because in addition to Island hopping there is thought to be evidence that some terrestrial species have (inadvertantly) spread from one landmass to another by rafting on floating conglomerations of vegetation – even trans-Atlantic dispersal by this mechanism is considered a likely explanation for the spread of some genera. Because such events will have been rare, and successful only by chance, it's difficult to put numerical constraints on the limits to their possible success. {The poster formerly known as 87.81.230.195} 2.219.34.253 (talk) 05:09, 24 July 2018 (UTC)

What about big animals like deer, elephants and bear? Wouldn't they not want to get on cause there's not enough food and freshwater and it might not be able to support their weight? And there must be other animals that wouldn't have their range extended by vegetation rafts, i.e. perigrine falcons maybe? Would they have an interest in making a long voyage on a raft where they can't hunt by slamming animals into the ground? Sagittarian Milky Way (talk) 19:08, 24 July 2018 (UTC)

Peregrine falcons can be blown off course and like any other bird - there are several records of them on Tenerife [17] for instance as vagrants. Mikenorton (talk) 20:16, 24 July 2018 (UTC)

SMW, you are attributing deliberate forward planning to non-sapient creatures, in a scenario where even H. sapiens would not be able to forecast an outcome. Animal dispersion by rafting is purely accidental, with animals inadvertently stranded on such rafts (which can be quite large) very occasionally being lucky enough to survive long enough to come within reach of land again – only one "success" in a million years might be enough to trans-oceanically disperse a given species.

Keep in mind that many large animals can swim surprisingly long distances if they choose, or are forced, to: Elephants have been seen swimming in the Indian ocean miles from land (see also Elephantidae#Evolutionary history); Polar bears routinely swim tens of miles, (and other bears can probably swim quite well); while Scandinavian Elk (aka Moose) are now known to dive several meters in order to feed on lake-bottom vegetation and coastal seaweed. Even sloths have been observed swimming! {The poster formerly known as 87.81.239.195} 90.218.111.216 (talk) 09:54, 25 July 2018 (UTC)

July 24

Removing water to connect all current land...

How much would the sea level have to drop to have all *current* above the water land to be connected by land? And what would be the last piece of current land to be connected?Naraht (talk) 15:14, 24 July 2018 (UTC)

Does that include middle-of-the-ocean features such as Hawaii? ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:31, 24 July 2018 (UTC)

Yes. And Pitcairn, Bermuda, Kerguelen, etc....Naraht (talk) 15:33, 24 July 2018 (UTC)

To connect Mauna Kea to mainland, you would have to drain several miles of water. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:47, 24 July 2018 (UTC)

Any idea how to get more accurate information? (A decent map of depths of the Pacific would probably help, but I haven't found a great one) For Hawaii, it is entirely possible that the land bridge that gets revealed connects Mauna Kea to Kamchatka along the Hawaiian–Emperor seamount chain, but I'm not sure on the depths of some of the gaps in the chain?Naraht (talk) 18:02, 24 July 2018 (UTC)

In Google Images, there are various topographic maps of the ocean floor. This NG item[18] allows you to look at portions of it. The Hawaiian Ridge is a series of volcanoes which go way down deep, as are many of the other Pacific islands. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:33, 24 July 2018 (UTC)

Agreed, but the question is whether there are gaps in the Hawaiian-Emperor that go all the way down to the general seafloor or whether it stays significantly above that level as is true between Hawaii and Oahu.Naraht (talk) 19:46, 24 July 2018 (UTC)

You can download a detailed (30 arc second) grid of global bathymetry from GEBCO here. With the appropriate software you could mess about with a colour bar until you found what you were looking for. Mikenorton (talk) 19:57, 24 July 2018 (UTC)

In case you didn't know: Puerto Rico is surrounded by water. 2600:8806:4802:C700:19EF:9053:95DC:1C0A (talk) 21:05, 24 July 2018 (UTC)

Thanks, Donald. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:15, 24 July 2018 (UTC)

A related question [19].--Wikimedes (talk) 05:48, 25 July 2018 (UTC)

How do weeds manage to grow without a drop of water in the soil?

Not a drop of rain in two months, and yet I have to remove weed in the garden. I need to water the plants to prevent them from drying out in these extremely dry conditions, yet the weeds germinate and grow. How do these plants get enough water? Count Iblis (talk) 15:48, 24 July 2018 (UTC)

It's at least partly a circular problem: plants are called weeds because they grow where they're not supposed to. Plants with higher tolerance for dehydration would have an advantage filling that niche, so it makes sense that many weeds would survive/thrive while other plants dried out and died - if they didn't, they wouldn't out-compete your tomatoes and dahlias. So what makes them dehydration tolerant? Well, there are many adaptations that will play a part (pore placement and density, gross morphology, waxy coatings, the use of taproots, and so on. Weeds rarely spend a lot of energy on fleshy fruit or showy blooms (though there are some exceptions), and that also reduces their need. Matt Deres (talk) 16:21, 24 July 2018 (UTC)

Are you sure they're not coming up from the roots of weeds you've previously tried to remove? Anyway I've heard weed is associated with Satanism so it must be able to cope well with the heat ;-) Dmcq (talk) 16:24, 24 July 2018 (UTC)

There are indeed plants with deeper roots, but I'm puzzled about new weeds that germinate and have tiny roots when I pull them out. Somehow these tiny roots were able to extract water from the bone dry soil. So, it must be what Matt Deres says about losing less water than other plants, but there must also be mechanisms that allow water to be extracted from the top layers of the soil. Perhaps some of the water at greater depths in the soil evaporates and at night when the top layers of the soil cool down, the water vapor makes it there via pores and condenses there? Count Iblis (talk) 17:17, 24 July 2018 (UTC)

I suppose some weeds are better at conserving water but I think most just are far better at extracting the water and leaving the soil too dry for other plants - it is a major way they outcompete other plants I believe. Dmcq (talk) 17:50, 24 July 2018 (UTC)

If actual data doesn't match your assumption, it is quite likely your assumption is wrong. You have assumed the soil has zero water. Plants are growing in it. Therefore, your assumption is wrong. To have assumptions impervious to contrary evidence is a problem... --Jayron32 18:02, 24 July 2018 (UTC)

One way to get water in the top of the soil is via dew or frost. Before sunrise the soil surface may be moist, but when you look in the afternoon all that moisture may have evaporated. Graeme Bartlett (talk) 03:11, 25 July 2018 (UTC)

Deploying Compost in Extreme Heat.

I know that in the UAE and Saudi Arabia when farmers plant they have little water retention in sandy soils. Why cant they just compost all the organics from the big cities or ship in organics from other places for composting and plant in that. Is there something specific that happens to high organics soils(IE. Compost) when it is exposed to dry heat? Is this sustainable. Looking for someone to prove sustainability or not. If you have questions on more info Please Ask. — Preceding unsigned comment added by Mason201 (talk • contribs) 17:10, 24 July 2018 (UTC)

[ http://hal.cirad.fr/docs/00/18/03/35/PDF/Bahri.pdf ]

Abstract:

Water reuse in Tunisia: Stakes and prospects. In the arid and semi-arid region, countries like Tunisia are facing increasingly serious water shortage problems. According to forecasts, increased domestic and industrial water consumption by the year 2020 may cause a decrease in the volume of fresh water available for Tunisian agriculture. It is therefore important to develop additional water resources as well as protect the existing ones. One way to cope with these problems is to reuse wastewater in agriculture. Therefore and before launching the water reuse policy, a research program was undertaken...

--Guy Macon (talk) 17:44, 24 July 2018 (UTC)

Composting requires the presence of air. Water is needed in the right amounts to maintain activity without causing anaerobic conditions; the air/water balance is critical to maintaining high temperatures (135°-160° F / 50° - 70° C) until organic solid wastes decompose. Urine, itself useful as a nitrogen-rich fertilizer, is a suitable additive to a compost pile. DroneB (talk) 17:46, 24 July 2018 (UTC)

In addition to that, an obvious question is, why compost in the desert anyway? I mean the idea of composting waste from their own cities may make some sense. But what's the purpose of shipping in organic waste from elsewhere? Maybe you've never composted but if you ever did you'd know that the volume of what you start with is a lot more than what you end up with. [20] So there are at least 2 and probably more (shipping organic waste around seems a good way to ensure lots of problems with pests etc) problems with shipping in the waste and composting it on site. If the idea made any sense, it would seem better to simply compost it somewhere else and ship in the compost. BTW perhaps Desert greening will be of some interest. You'd note that it doesn't really mention shipping in compost or soil at massive scale as part of the process. Nil Einne (talk) 23:05, 24 July 2018 (UTC)

Insect from eastern Quebec

Graceful insect

Hello. Can you identify this little fellow who landed on my front door this morning (or last night..). I live in Rimouski suburb, Quebec Canada, in an open landscape of bungalows, many trees and several patches of mixed forest, a few hundred meters of St-Lawrence estuary. Body length : 1cm, wings span 2,5 cm. Thank you. Dhatier (talk) 17:45, 24 July 2018 (UTC)

I'm pretty sure it's a type of paleoptera (i.e. mayfly, dragonfly, or damselfly), though a rather more ornate one than I have ever seen. Maybe that will lead you in the right direction, though there are thousands of different species. --Jayron32 18:12, 24 July 2018 (UTC)

Looks like a rose plume moth Cnaemidophorus rhododactyla. Mikenorton (talk) 18:19, 24 July 2018 (UTC)

Agreed. T shapes are usually some sort of plume moth (although our local ones are ghostly white). Andy Dingley (talk) 18:30, 24 July 2018 (UTC)

Cnaemidophorus rhododactyla confirmed by numerous images on Google. Thank you very much. Dhatier (talk) 18:45, 24 July 2018 (UTC)

July 25

Why can Labrador get so hot?

North West River Northwest River
The highest known North American temperature east of Ontario and New York happened here in 1914.
Coordinates: 53°31′31.32″N 60°08′41.80″W

List of extreme temperatures in Canada. Also has exceeded the all-time highs of DC, Philly, Toronto, Ottawa, Windsor, Detroit, O'Hare, Indianapolis and Columbus and only 0.9F less than Ontario (108F). Sagittarian Milky Way (talk) 22:48, 25 July 2018 (UTC)

Not a complete answer, but there were heat records in many parts of the world this year, with a crisis in Japan at the moment. Co2 levels also fluctuated less, remaining high (with average level higher every year). Extreme weather events are predicted to rise as global warming pursues. Forest fires are regular in many areas and increasing, dumping more Co2 and the warming of permafrost is a concern as more methane is not converted before reaching the surface (with a temporary effect higher than that of Co2). There are fears about reaching tipping points and it's very difficult to determine when one will be attained; runaway changes are considered possible when one or more such tipping points are reached. About Labrador this year specifically, I'll let others expand (obviously, specific events cannot directly be linked to global trends). —PaleoNeonate – 23:28, 25 July 2018 (UTC)

The highest known temperature east of Ontario and New York was not only so far north but also outside the modern warming era or the Dust Bowl which makes it even more unusual. Sagittarian Milky Way (talk) 00:40, 26 July 2018 (UTC)

I am intensely skeptical of that information. The table with that value was added on March 21 of this year, with no sources, by an editor who has repeatedly run into trouble due to adding unsourced information to articles. It is not uncommon for locations that are far inland to reach very high temperatures, even if they are far to the north, but for a coastal location to reach such a temperature would really be anomalous. Anything is possible, of course, but I would like to see some evidence. Looie496 (talk) 03:06, 26 July 2018 (UTC)

There really seems to be a record of that temperature, the Canadian government list it [21]. There is some similar scepticism of that temperature in this discussion [22] (which was how I worked out to use that site) and [23]. Nil Einne (talk) 12:18, 26 July 2018 (UTC)

Further found [24] and sort of [25]. This post in the first discussion [26] is most interesting as it includes a response from Environment Canada which included an image of the original paper record [27] confirming it's not simply a modern data entry error. (Although IMO one of the responses in that thread is a little harsh. It sounds like whoever responded primarily felt they were being asked if there was some data entry error and confirmed there wasn't with the original records. They may not have felt it worthwhile going through the process of annotating or removing a single potentially spurious record.) BTW, in case there is some remaining confusion because of PaleoNeonate's post, we aren't AFAIK talking about anything this year or as SMW said anywhere close to modern times but a record from 1914. Nil Einne (talk) 12:39, 26 July 2018 (UTC)

Wow. I still think there must be an error somewhere, though. As one of those linked posts says, if the high was 65 the day before and the day after, and it rained on that day, it's very difficult to imagine how the temp could have reached 107. Looie496 (talk) 14:04, 26 July 2018 (UTC)

One thing to remember is that climate is complex, and that temperatures (both averages and extremes) are only partly a function of latitude. You can see this sort of thing at U.S. state temperature extremes. The state with the lowest record high temperature? Hawaii. The state closest to the equator. This is true because temperature is a factor of many things, besides latitude there are wind currents, proximity to large bodies of water, temperature of that water, local terrain, elevation, etc. etc. Microclimates can also be similarly weird; one of the most famous microclimates in North America is San Francisco, which is frequently 10-20 degrees F colder than places only a few miles away; (There's a frequently mis-attributed aphorism that goes "The coldest winter I ever saw was the summer I spent in San Francisco") the average July high is 66.5F for San Francisco, and 72.0F for Oakland, a 5.5F difference is impressive given that the cities are connected by a bridge. All that goes to say that simply being far in the north does not disqualify some specific location in Newfoundland from having some unusual microclimate, given the variety of factors at play. --Jayron32 15:20, 26 July 2018 (UTC)

It might be useful to examine the temperature records of adjacent stations, also newspapers covering the area - these often contain a day-to-day weather record. See List of newspapers in Canada. Here are the figures for five stations in the area:

Date                  Station          Max (°C.)                       Min. (°C.)            
1914 August 11        Burin            23.9                            12.8
                      Fogo             23.3                            15.6 
                      North West River 41.7X                           10.0
                      St Georges       24.4                            15.6
                      St John's        23.9                            19.8

You will note the red "X" against the North West River maximum. This suggests it was picked up as an anomaly at the time. 86.133.26.146 (talk) 17:32, 26 July 2018 (UTC)

There is also a red X by the original data record for "107" above. Also note there is a column "Range" to the right, which has an entry "57" (which is "107" - "50"). The weather was given as some letter, which I assume means clear, for the morning, with "overcast" in the afternoon, and "rain and heavy thunderstorm" as a note. Which is what you'd expect with that kind of high temperature! Finally, note the sequence of high temperatures: 97 62 63 71 70 64 65 66 75 107+ 65 86 76 62 63 65 63 65 50 49 68 65 63 74 78 74 . Putting those in LibreOffice Calc and doing STDEV.S(that range of values) I get 12.41, which sounds at least about right. The average is 69.46, so this value is at 3.02 standard deviations out. That means there is only a 0.27% (1/370) chance of such a value occurring, according to standard deviation. (It seemed faster to check that table than remember the function name...) Nonetheless, in a dozen such months, one time it could happen by chance. The value is still suspect, of course, because any 1% chance of error is more likely than that it is correct (that is, until you read the post above; with confirmation, its chance of being correct is much higher than the 1% error) -- but we certainly don't know it is wrong. Wnt (talk) 22:27, 26 July 2018 (UTC)

To me it looks more like a + or straight cross than an x unless it was added at an extreme angle. See also this rotated version. [28]. I was thinking of it before and it seems to be a clear highlighting. But whether it was intended to indicate the value was in doubt or could be an error or an anomaly, or simply noting it was unusual high or maybe that it was the highest value, I'm not sure. I'm leaning towards it simply being because it's the highest value. There look to be two bars which similar denote the lowest minimum values. I was originally confused about these because I thought they were underlining two random values with nothing special. But looking more carefully I realised they are probably a bar above the two 38 values which are the lowest minimum values for that month. Nil Einne (talk) 10:21, 27 July 2018 (UTC)

Not sure why this doesn't break the Second Law of Thermodynamics

I'll assume it doesn't, but I can't see why. Advice welcome, I've been scratching my head for a decade.

Imagine the Earth were so far from the Sun, that there was no solar heating, and it had no internal radioactive decay ; would its atmosphere ( probably needing to be only Helium, to be a gas at 6 Kelvin ) be the same temperature on the surface, as at say 10 kilometres altitude ? If so, how would a molecule of air moving vertically, in the Earth's gravitational field, keep the same kinetic energy ( and hence velocity and hence temperature ), as it gained or lost the gravitational potential energy, of that 10 km of height ? Air molecules may well interact, sharing and equalising their kinetic energy ; but over any finite change of height, there must be an equal and opposite change of kinetic energy. If this were not true, a molecule of air which was moving upwards, would continue at the same speed, indefinitely, until it escaped to space ; and that would seem to break the even-more unbreakable First Law.

If the gas particles do exhibit "ballistic" behaviour ( like mortar shells ), and this maintains a permanent temperature gradient with height, which could be used to drive a heat engine ; a planet with such an atmosphere, could continuously generate mechanical power, as it absorbed heat energy from the 6 Kelvin afterglow of the Big Bang.

The continuous absorption of heat to generate power, would seem to break the Second Law.

Thanks. GeoffAvogadro (talk) 23:21, 25 July 2018 (UTC)

I think you're getting lost in complexities, but the clean and simple answer is that air temperature decreases with height: this is called the adiabatic lapse rate. The physical reason for this is that at lower altitudes, there is more gravitational potential energy; at higher altitudes, individual molecules have expended kinetic energy to work against gravity.

There are many confounding extra details that make atmospheric science so much fun; but at the basic level, there absolutely is a statistical reduction in kinetic energy for air molecules as their altitude increases.

Above a certain height, the sparsity of the gas molecules becomes very low, and some different properties of thermal and chemical physics begin to dominate: this region is called the ionosphere (and/or the thermosphere, or magnetosphere, depending on which classification scheme you're using; these terms are sometimes used interchangeably, but they actually specify sub-regions that describe the details of the molecules and ions at specific altitudes and atmospheric conditions).

Nimur (talk) 23:34, 25 July 2018 (UTC)

The answer is that in that scenario the entire atmosphere would be in thermal equilibrium with the cosmic background radiation, at a temperature of 2.8 K. But basically there wouldn't be any atmosphere -- even helium would be in a liquid state at that temperature. You would only have a few stray molecules that randomly escape from the surface, hardly denser than outer space. Looie496 (talk) 02:45, 26 July 2018 (UTC)

Helium is a liquid at that temperature at atmospheric pressure. You'd need to check the phase diagram of helium to see what state it would be in at the pressures you are thinking of. Also, if helium is escaping from the surface and dissipating into the atmosphere at a greater rate than it is condensing, it is not in equilibrium; your planet is losing mass, which means even at the same temperature, you're losing thermal energy. --Jayron32 18:03, 27 July 2018 (UTC)

Good point about pressure. Looking at the phase diagrams at http://ltl.tkk.fi/research/theory/helium.html, it appears that at the cosmic background temperature, you could have an atmosphere of up to two Earth-atmospheres in pressure composed almost entirely of ³He, above an ocean of liquid helium. The other stable isotope, ⁴He, would be liquid down to a much lower pressure. Looie496 (talk) 20:42, 27 July 2018 (UTC)

It is true that in the absence of surface heating the atmosphere will gradually become isothermic. So, there is no contradiction with the second law. Molecules going up will be slowed by the gravity but will gain energy in collisions with molecules going down and therefore accelerated by the gravity. This picture is only true on spatial scales above the mean free path length in gas. Below this length the gas kinetic model (and thermodynamics generally) is not applicable and the gas behaves like a cloud of free particles which happens, for example, in exospheres. Ruslik_Zero 06:46, 26 July 2018 (UTC)

Uh, unless there's some subtlety I'm missing here, you couldn't drive a heat engine with the atmospheric temperature gradient because to move the hotter air away from the surface you have to do work against Earth's gravity. Also, I know this is a spherical cow kind of thought experiment, but as Looie496 noted, at that temperature you'd just have frozen volatiles on the planet's surface, with a tiny amount of sublimated vapor, as seen on worlds like Pluto. And there'd be no appreciable amount of helium; Earth's gravity is too weak to hold on to hydrogen or helium. --47.146.63.87 (talk) 06:59, 26 July 2018 (UTC)

I thought that the cosmic background radiation plus starlight gave a higher equilibrium temperature than the cosmic background radiation alone. Obviously this would differ (in the galaxy core? in the empty spaces between galaxies? Any large clouds nearby?) but the interesting number would be for a planet in the spiral arm, roughly where our sun is. --Guy Macon (talk) 06:59, 26 July 2018 (UTC)

Assuming the background temperature was enough to keep helium a gas then the temperature of the air would be the same at all heights. It being different on earth is because the earths atmosphere is nowhere near an equilibrium, we have the sun shining down and various interactions between the gas and the radiation. The energy of the molecules would get spread out, they don't just fall from space to the ground. Just having molecules falling straight up and down isn't a stable equilibrium. Dmcq (talk) 11:37, 26 July 2018 (UTC)

July 26

Stomach usually gurgles on the left side

This question is not for diagnosis but for curiosity. I hear that my stomach usually gurgles on the left side rather than on the right. Why most of the gurgles occur on the left side rather than about the same on both sides? PlanetStar 05:32, 26 July 2018 (UTC)

Your stomach is mostly on the left side of your body. --76.69.47.228 (talk) 05:47, 26 July 2018 (UTC)

But the gurgles sometimes occur on the right side of the abdomen. The stomach were referring to is a bean-shaped organ above the intestines. The gurgles doesn't just occur in the stomach, it also occurs in the intestine, which is evenly spread from left to right. Maybe most gurgles occurring on the right side is intestinal gurgles, but maybe most intestinal gurgles occur on the left side; if so, what's the cause of occurring mostly on one side of the intestine? PlanetStar 04:33, 27 July 2018 (UTC)

I suppose that what is gurgling is not the stomach as a whole but the pylorus, which is clearly located on one side of the body, by most humans the right one. Maybe you have it on the other side? Also gurgling of the intestine is possibly not evenly distributed but happens e.g. only at the interface between colon and ileum, or only in its descending or ascending but not horizontal segments. 194.174.76.21 (talk) 16:07, 27 July 2018 (UTC) Marco Pagliero Berlin

Not eating or drinking before surgery

A family member had to have several minor surgeries, I made a comment to the doctor that "your instructions said no food or drink after midnight for a 7AM surgery, and later we got the exact same instructions for a 5PM surgery." To his credit, he listened and now gives the instruction "no food for ten hours before the surgery, and no water for four hours before the surgery". Needless to say, we follow the instructions no matter what they are. Only an idiot ignores doctors orders.

This got me to thinking and researching. I believe that these restrictions are to reduce the chance of you vomiting while under anesthesia and then sucking some of that stomach acid down your windpipe. So has anyone done a study about how long food and water stay in the stomach? And does the sphincter valve that empties the stomach slowly meter out the contents to the intestines or does it let the stomach work on the food for a while and then dump the result into the intestines? Please note that I am asking for sources, not opinions. --Guy Macon (talk) 06:53, 26 July 2018 (UTC)

You are correct about the purpose: see nil per os and aspiration pneumonia. Chyme states, with no given source: Depending on the quantity and contents of the meal, the stomach will digest the food into chyme in anywhere between 40 minutes to a few hours. However, you can vomit material from the small intestine if vomiting is sufficiently vigorous; such vomiting can often be identified by the presence of greenish bile in the vomit. It sounds like they want all food to have passed into the large intestine. --47.146.63.87 (talk) 07:10, 26 July 2018 (UTC)

Thanks! Good info. I see that Nothing by mouth says "The American Board of Anesthesiology recommends that patients should not eat solid food for at least 8 hours prior to a procedure, and should not drink even clear liquids for at least 2 hours prior". Looks like the doctor added a couple of hours to that just to be safe. Also, he has you show up two hours before the surgery and they put you on an IV, so from a standpoint of thirst/dehydration its only two hours with no water.

As a passing note, if the stomach empties too quickly after for instance gastric reduction surgery it causes the imaginatively named Dumping syndrome, not a pleasant experience. Richard Avery (talk) 12:30, 26 July 2018 (UTC)

Does anyone know how long it takes for food to get past the "vomiting from the small intestine" state? And whether it can happen under anesthesia? --Guy Macon (talk) 17:42, 26 July 2018 (UTC)

I'm not finding anything definitive and searching has already ruined my lunch. :) I will point out the article on fecal vomiting, which suggests that, in rare cases, there is not really a limit (unless it's already pooped out the other end). Matt Deres (talk) 17:44, 27 July 2018 (UTC)

Small intestine transit time ranges from 15 minutes to 5 hours. In 83% of those studied, transit time was less than 2 hours, and mean transit time was 84 minutes. [29] Probably once you're past the duodenum the exit route will no longer be up. - Nunh-huh 17:58, 27 July 2018 (UTC)

Seeking an identification for this caterpillar found in garden. Somerset UK

Hi folks

I found this caterpillar in the garden this afternoon and I'm hoping someone can identify it. It was about 4 inches inches long and fairly thick. I've attached some pics the last of which was after I had gently brushed against it with a twig, this appears to have made it change it's head shape into something broader and more threatening, as a defensive measure no doubt.

This was all happening in Somerset UK in case that helps identify the creature.

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Many thanks Gareth — Preceding unsigned comment added by Hermitical (talk • contribs) 20:18, 26 July 2018 (UTC)

Looks like a Deilephila elpenor, an Elephant Hawk Moth.Mikenorton (talk) 20:52, 26 July 2018 (UTC)

(ec)I googled "caterpillars with segments that look like eyes" an this ite turned up: [30] They actually think it looks like a snake. Be that as it may, they're saying it's the "Deilephila elpenor, known as the Elephant Hawk-moth". ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:53, 26 July 2018 (UTC)

And given Mikenorton's confirmation, it looks like you've got some new illustrations to add to the article! ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:55, 26 July 2018 (UTC)

Many thanks for all your help. It was an incredible sight! Do you really think I should add any/all of these photos to the Deilephila elpenor article? Hermitical (talk) 18:04, 27 July 2018 (UTC)

You could add them to commons:Category:Deilephila elpenor (caterpillar). Mikenorton (talk) 18:30, 27 July 2018 (UTC)

July 27

Definition of episomal

Is it correct to call a non-integrating plasmid episomal if it's in a eukaryotic cell and does not replicate in that cell? Is the ability to replicate in the cell in question necessary to meet the definition of episomal? Thanks. --185.230.100.66 (talk) 06:28, 27 July 2018 (UTC)

The ability to replicate independently of the nucleus is the defining characteristic of Plasmid DNA, while some suggest that the term episome be abandoned or modified to refer to viruses that may be replicated in the nucleus, see Plasmid#Episomes. DroneB (talk) 12:57, 27 July 2018 (UTC)

AA and KSD

Every aldosterone antagonist that I see is also a potassium-sparing diuretic. Are there any aldosterone antagonists that are not potassium-sparing? 209.149.113.5 (talk) 18:46, 27 July 2018 (UTC)