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# March 21

## Immune system questions.

If we moved into a low-bacteria environment, does that make our immune system weaker to bacteria? Like, does our immune system lose their resistance to bacteria? I ask this because I know this is the case for allergies. I happen to be cat-allergic, got my 1st cat at age 12. Took only 2 days with some allergies. Then lived and cuddled with the same cat for 6 years. 18, went to college for a year, came back, immediately allergic to my cat. Red eye, running nose, and in a 3-week period was not enough to recover. That my immune system was stronger at age 12 than age 18 is standard. Years later expose to cat for lesser periods, can still fight it off, but will lose allergic-resistance to cats if not exposed for some time. But that's not my q. My q is about bacteria. Supposed someone moved into an apartment and bleaches the walls, floors, and doorknobs. Stores toothbrush in hydrogen-peroxide water solution, mouthwashes every day, hand sanitizers. Does that make their immune system weaker to bacteria so if they leave the environment and venture onto the public?

So as a 2nd question, is our body's immune system to bacteria, separate to the immune system to allergies? Meaning, 1 can have a strong immune system to bacteria but weak to allergies, or strong to allergies but weak to bacteria? Supposedly a person hit with chicken-pox becomes immune to it for life (or at least a good 50 years). I also happen to be motion-sickness naturally, and can temporarily be immune to that. If I read while in car, feel sick to throw up, then can read in car the next day. However, if I don't read in car for a year, I have to restart that resistance. But does that mean humans have to constantly be exposed to all kinds of bacteria in order to stay immune from them? 67.175.224.138 (talk) 11:49, 21 March 2020 (UTC).

See: Allergy, Hygiene hypothesis and Immune tolerance. Allergies are the result of the immune system malfunctioning and becoming being hypersensitive to harmless substances in the environment. The Hygiene hypothesis suggests that this may be the result of the immune system not being challenged enough in early life. Motion sickness is nothing to do with the immune system. Presumably your system of balance becomes habituated to the motion of a car the more often you experience it. Richerman (talk) 19:55, 21 March 2020 (UTC)
People can become habituated to a particular cause of Motion sickness (there are several) on a temporary basis without this habituation becoming permanent. Horatio Nelson notoriously suffered from seasickness for several days every time he embarked after a period onshore, throughout his life. {The poster formerly known as 87.81.230.195} 90.197.27.39 (talk) 10:45, 22 March 2020 (UTC)

Anyways, I didn't ask about immune system immunity to viruses cuz I already know the answer. I happen to explore sewers. Got sick from the norovirus and rotavirus floating in the moist air, got gastroenteritis. Then when recovered, go right back into the tunnels because got immune to them. 4 years later, got sick again, but maybe 75% as bad. Asked a microbiology professor, why is that? Did I lose my immunity? The answer is viruses change over time. But what I don't know is if bacteria changes over time. If it does, then I imagine it's good to stay in a regular-bacterial environment. Now if viruses stays the same for 20 years, can your immunity stay the same? No way to test. But if bacterial stays the same for 20 years, do we lose immunity to it if we leave their environment for some time and come back? Just like my cat allergies, or motion-sickness. 67.175.224.138 (talk) 18:07, 23 March 2020 (UTC).

## Mixing soap and bleach

Mixing bleach with a cleaning stuff can be dangerous. Is it safe to mix soap and bleach? This is ordinary soap like soap bar. Soap I use is made by village people from olive oil cut into blocks. Also, if I add bleach to soapy water like % 0,2 solution will be better disinfecting surfaces? Thanks Hevesli (talk) 20:31, 21 March 2020 (UTC)

Since the pH can vary, and the presence of ammonia compounds is unknown, it would be prudent not to mix bleach with bar soap. There are several sources warning against mixing bleach with other cleaners, including dish soap (e.g.). It would be better to clean with soap, then use a bleach solution as a rinse to disinfect. 2606:A000:1126:28D:D137:5FBD:51AA:C141 (talk) 21:17, 21 March 2020 (UTC)
• Don't mix hypochlorite bleaches with acids - it releases chlorine, which is an irritant, maybe toxic in quantity, has even been fatal. Soaps are alkaline, not acidic, so this is OK.
But I'd still ask why? As a general principle here, do one thing, and do it well. You don't need to soap-and-bleach, just use soap. Andy Dingley (talk) 00:05, 22 March 2020 (UTC)
Although ammonia is basic, mixing bleach with ammonia produces toxic and potentially deadly[1] chloramine vapours. Ammonia can be used in soap production.[2] If someone makes a calculation error (or uses the amounts that are proper when using pure olive oil but uses olive pomace instead), the finished product may still contain some (chemically active) ammonia. I am fairly certain, though, that the smell would give this away, and certainly if the smell is not masked by perfume, as it is unlikely to be in rurally home-produced soap. So if the soap has no pungent smell, there is no real risk. Chloramine vapours give off the familiar "chlorine smell" of swimming pools, so that should also be a warning to open the windows. Regular soap does not kill bacteria; at best it washes them away. By itself, a cocktail that both cleans (acts as a surfactant) and kills microorganisms is a good idea. It is the basis of antibacterial soaps, which add an antibacterial ingredient to liquid soap.  --Lambiam 09:23, 22 March 2020 (UTC)
• You might as well argue that if someone made "soap" with metallic sodium instead of the hydroxide, that would be a bad idea to mix with hypochlorite bleaches! A failed "soap" with free ammonia at the end isn't soap, it's chemical waste. Andy Dingley (talk) 11:48, 22 March 2020 (UTC)

## Germany, Netherlands and COVID-19

In 2019–20 coronavirus pandemic article I read for Germany 22.213 cases with 84 deaths is % 0,38. But for Netherlands 3.640 cases with 137 deaths is % 3,8. So is 10 times more! How can this be understood, please? Hevesli (talk) 20:57, 21 March 2020 (UTC)

We won't know until the pandemic has run its course. ←Baseball Bugs What's up, Doc? carrots→ 21:00, 21 March 2020 (UTC)
We can figure out a lot of things about the universe while it goes on, and the same is true for the current pandemic. With respect to the original question, there are at least educated guesses. The German Robert Koch Institute maintains that in German, the ratio of detected/reported cases to undetected cases is rather low, i.e. a large fraction of all cases are known. More severe cases are, usually, detected and reported everywhere. So if Germany detects more of the mild cases, the fraction of deaths seems to be lower. Another possible (and communicated) reason is that Germany has a decent health care system, and in particular has a lot more ICU beds with respirators per population than most other countries. --Stephan Schulz (talk) 21:27, 21 March 2020 (UTC)
Netherland has a decent health care system too and no shortage of IC beds (not yet, at least). But in Netherland only the patients sick enough to require hospitalisation are consistently tested, others are considered suspected Covid-19 patients and requested to quarantine themselves, but not counted. Another factor may be that Dutch doctors often don't treat patients if they consider the probability of success negligible (where surviving in a vegetative state isn't considered success). This means that the hopeless patients are not sent to IC and may die a few days sooner, which, given the exponential growth of the epidemic, leads to an apparent increase in death rate. (Don't worry, if the patient (or his relatives) insist on treatment, the doctors will do what they can.) PiusImpavidus (talk) 11:32, 22 March 2020 (UTC)
There is an article about this (with some speculation as to the reasons) here: https://www.theguardian.com/world/2020/mar/22/germany-low-coronavirus-mortality-rate-puzzles-experts Iapetus (talk) 10:13, 23 March 2020 (UTC)
If you can understand German, there also is a good YouTube video by Harald Lesch (a professor of Physics an LMU in Munich and one of the better known science communicators in Germany). There is some overlap with the Guardian article, in particular the sampling bias. In Germany, with early testing, many of the identified carriers are young and fit people returning from Skiing, and their circles. In Italy, testing was primarily driven by people presenting with a serious illness. I don't know how this compares the the Netherlands, though. --Stephan Schulz (talk) 16:49, 23 March 2020 (UTC)

## CT scan coronavirus diagnosis

Chess grandmaster Irina Krush (in NYC area, I believe) reported:[3]

So I went to the ER (not the most pleasant experience, there were people around with a cough so severe I was really concerned I could catch the virus there). Anyway, the CT scan showed "early coronavirus" and pneumonia in both lungs. I was also given the actual test, which only came back today (positive). I spent a couple days in the hospital, I guess mostly under observation as there wasn't much that needed to be done for me...they did test my blood for oxygenation and found it was fine. So now I am home...taking the hydroxychloroquine tablets.

She is recovering at home now and seems to be doing ok. I thought it was interesting that she is being treated with hydroxychloroquine which I thought was still in clinical trials. I also had never heard of CT scan as a diagnosis for virus. Is that a thing? Thanks. 2601:648:8202:96B0:386A:A40C:EBB1:ACC0 (talk) 23:56, 21 March 2020 (UTC)

About hydroxychloroquine, aren't you the same person who asked #Coronavirus drugs where replies extensively discussed such off label usage? In any case, I'm not sure if there is anything to add that wasn't already mentioned there.

On the other issues, our Coronavirus disease 2019#Diagnosis and the more specific COVID-19 testing article has a fair amount of info on CT testing. As it sort of indicates, despite one limited early study claiming the ability to distinguish SARS-CoV-2 infections from other forms of pneumonia, this isn't well accepted. Therefore AFAIK, most health authorities would not label such a case as confirmed case absence of laboratory (RT-PCR at this stage) confirmation. See e.g. the WHO's definitions [4] or this NZ one [5]. I think this even applies to the Chinese CDC but I'm unsure.

However the CT scan results probably combined with other symptoms may be enough to indicate laboratory testing depending on the health authority or doctor involved, maybe even without exposure to a known case. And those especially when combined with exposure to a confirmed case may be enough for a probable case if laboratory testing either could not be performed or was inconclusive and other possible causes have been ruled out. This isn't unique to COVID-19 see e.g. this for MERS [6] but as far back as SARS there was the same thing.

BTW, I would urge very strong caution from reading too much into that paper on CT scan results. The paper itself mentions limitations at the end. More generally, it's doubtful there were CT scans of people with mild symptoms.

Nil Einne (talk) 03:31, 22 March 2020 (UTC)

Thanks, and yes that was me the other day. This question was mostly about the CT scan and thanks for the info about it. Yes I understood about off-label hydroxychloroquine but still found it interesting that it's being prescribed in "retail" medicine (CityMD) already. Those places are usually rather behind the curve. 2601:648:8202:96B0:386A:A40C:EBB1:ACC0 (talk) 05:28, 22 March 2020 (UTC)
Numerous health authorities have warned against using hydroxychloroquine for COVID-19 outside of clinical trials except potentially as a drug of last resort in people given extensive treatment who still appear likely to die. Drugs are not benign harmless things that can never cause adverse effects. Unfortunately doctors don't always follow "best practices". There is no U.S. law against off-label prescriptions, and the drug is already available for other conditions, so nothing prevents a doctor from prescribing it for COVID-19. Indeed, there have even been reports of dentists prescribing it for themselves or others to stockpile it, which has lead to a shortage. People don't always act rationally when they panic. (Note that some off-label uses of drugs are widely accepted based on evidence; this is not presently one of them.) --47.146.63.87 (talk) 05:42, 25 March 2020 (UTC)

# March 22

## Request for comment: The rest frame of the Cosmic Microwave Background (CMB) radiation might be the kinematic time-dilation minimising velocity and the key to understanding the twins "paradox"

Unfortunately the following comment was deleted from the talk page of the twins paradox article before anyone had a chance to reply.

Could the twins-paradox be explained by considering that kinematic time-dilation might be a function of velocity relative to the rest-frame of the CMB?

In a sense, observers who are "stationary" here on Earth, ARE the travelling-twin from the twins-paradox, because we're moving relative to the CMB, we're moving due to the rotation of the earth, the orbit of the sun, the galactic orbit, and due to inter-galactic attraction. Acceleration in the opposite direction (up to a point), could be thought of as a return to "stationary", and might result in a speed-up of time relative to Earth-time, just like when the travelling-twin in the twins-paradox returns to Earth.

In theory we could test this experimentally, perhaps by using a linear accelerator and taking two or three sets of measurements 6 or 12-hours hours apart when the linear accelerator is pointing in a different direction due to the rotation of the Earth. In theory, the accelerated particles should be going ever so slightly slower relative to the Earth for a given input power when the linear accelerator is pointed in the direction of our motion through the CMB. Alternatively, at a given particle speed relative to Earth, their half-life should be greater when the linear accelerator is pointed in the direction of our motion through the CMB compared to when it is pointed in the opposite direction. Alternatively, there might be some other non-zero kinematic time-dilation minimising velocity. — Preceding unsigned comment added by MathewMunro (talkcontribs) 00:16, 22 March 2020 (UTC)

The Twin Paradox is adequately explained by general relativity. The twin on earth is stationary, the travelling twin necessarily has to accelerate multiple times. If the CMB rest frame was a privileged frame of reference, that would be easily detected in e.g. Michelson–Morley style experiments, and we should also see different life times for cosmic-ray-induced muons on different sides of the Earth. Since GR is about the most thoroughly tested theory in history, either of these would be well-known. So: No. ;-) --Stephan Schulz (talk) 04:42, 22 March 2020 (UTC)
Firstly, on a somewhat semantic matter, the twins paradox concerns special relativity, not general relativity.
Secondly, Michelson–Morley experiments aimed to detect variations in the speed of light. I am not proposing a variable speed of light. I am proposing that there may be a non-zero kinematic time-dilation minimising velocity with respect to observers on the surface of the Earth, and that it may be the opposite of our velocity through the CMB.
Regarding why it may not have yet been detected: The speed we are travelling through the CMB is a fairly small portion of the speed of light (0.0012c), so the effect would be very subtle, (a Lorentz factor of 1.0006 vs the rest frame of the CMB presuming the rest frame of the CMB is the absolute minimum time-dilation velocity). Also, because of the way relativistic speeds are added together non-linearly, the effect on the Lorentz factor and half-life of particles moving at relativistic speeds would be much smaller than that - for example, if a muon were travelling at 0.9997c relative to the CMB, the Earth's motion through the CMB at 0.0012c would only increase the muon's velocity relative to us to 0.9997007c, and that would only increase the Lorentz factor from 40.8279 to 40.8756, with the difference being even less noticeable if the direction of travel of the muon were not aligned to or opposite the direction of Earth's motion through the CMB, and there is significant variation in natural phenomenon like observed half-lives and Muon flux, so it could be easily written-off as "background noise". Also, in most studies of kinematic time-dilation, the effects are entangled with gravitational time-dilation. Also, the CMB dipole was only discovered very recently, and before its discovery no one would have known which axis to look for a difference in the magnitude of time-dilation for a given speed relative to an observer on Earth's surface. And lastly, the fact that there have been so many tests of relativity already makes it harder to get support for another test.
Interestingly, I just located an article that claims: "... the duration of Muon decay, which should be a constant, definitely appears to shorten gradually from 1946 to 2017 from very roughly 2.330 microseconds (1946) to very roughly 2.202 microseconds (1963) to very roughly 2.078 microseconds in 2017" - http://www.gravwave.com/docs/V9%20Analyses%20of%20Muon%20Decay%20to%20Journal%20SS&T.pdf
Another study found: "The data showed a small but generally constant increase in muon generation during daylight hours when compared to night hours" - https://www.i2u2.org/elab/cosmic/posters/display.jsp?name=fluxvstimeofday.data
Both those observations could be explained by changes in the velocity of the observer with respect to the CMB if we throw out what we think we know about relativity and time-dilation.
In any event, the study of Muon decay would be a poor test of my postulate, compared to a linear-accelerator based test, because there appears to be numerous factors affecting Muon flux, such as solar wind speed & density & magnetic field fluctuations, see http://taurus.unicamp.br/bitstream/REPOSIP/73227/1/WOS000310911300066.pdf— Preceding unsigned comment added by MathewMunro (talkcontribs) 06:10, 22 March 2020 (UTC)

## Is it gravitational potential energy, or the strength of gravity that determines time dilation?

Unfortunately the following comment was deleted from the talk page of the Gravitational time dilation article before anyone had a chance to reply:

It seems implausible to me that time dilation would be based on the distance from the centre of a massive object, including when inside the bounds of the object where gravity is less than on the surface, rather than being based on the strength of gravity. I expect that the gravitational time-dilation at the centre of the Earth would be zero, because gravitational forces are zero, yet the article suggests that's where gravitational time-dilation is locally maximised.

Has anyone ever tried taking an atomic-clock to the bottom of a very deep mine shaft, where gravity is lower than on the surface of the Earth, and comparing it to an atomic clock that is on the surface, ideally at a different latitude, an equal distance from the earth's axis, so that it is travelling at the same speed? If not, someone ought to, because it is hard to be certain of anything if we don't try to experimentally isolate the effects of kinematic time-dilation and gravitational time-dilation. — Preceding unsigned comment added by MathewMunro (talkcontribs) 00:19, 22 March 2020 (UTC)

Normally we think of the gravitational potential as a positive quantity that increases with the distance to a massive body. However, this makes the gravitational potential of a point in space dependent on the specific body (such as Earth or the Sun) relative to which that distance is taken. In this context we need a quantity that is independent of any specific body. We must use a position infinitely (or very) far away from all masses as the fixed reference location with respect to which the potential energy is defined. At that reference location, there is no gravitational time dilation. As an observer approaches a massive body, the time dilation increases. Suppose they now enter a very very deep mine shaft. Do you think it plausible the time dilation will now decrease? I don’t know if your proposed experiment has been performed in that form, but those that have would have revealed that the formulas are off if "the strength of gravity" was the determining factor.  --Lambiam 04:31, 22 March 2020 (UTC)
Why not put it to the test, it would be a very cheap and easy experiment to conduct, and it could almost completely isolate gravitational time-dilation from kinematic time-dilation. — Preceding unsigned comment added by MathewMunro (talkcontribs) 07:16, 22 March 2020 (UTC)
If it is a very cheap and easy experiment to conduct, why not conduct it yourself? Just borrow two atomic clocks and head to a mine shaft. Do you think putting clock #1 at ground level and clock #2 at a distance d deeper will reveal anything not revealed by putting clock #1 at a height of d above ground and clock #2 at ground level? Since the experiments conducted already confirm the existing theory (within experimental error) and thereby disprove your theory, I'm afraid that if you cannot conduct the experiment yourself, you'll have to bribe or blackmail a team of experimental physicists, since otherwise they have no incentive for doing this futile exercise.  --Lambiam 08:42, 22 March 2020 (UTC)
You wrote "Do you think putting clock #1 at ground level and clock #2 at a distance d deeper will reveal anything not revealed by putting clock #1 at a height of d above ground and clock #2 at ground level?"
That is not what I proposed. I proposed moving clock #2 to a different latitude, so that it is the same distance from the Earth's axis, and therefore travelling at the same speed as clock #1, but at a different gravity.
Simply raising clock #1 above clock #2 would not achieve the same result for two reasons, firstly the speed that the two clocks are travelling at due to the Earth's rotation would be different, so you would face the problem of muddled special and general relativistic effects. Secondly, it would not reveal whether or not it is the strength of gravity or the distance from the centre of mass of the Earth that is the determining factor in the degree of time dilation as it would in the experiment I propose.
Of course, the act of moving the clocks into position itself would introduce some kinematic time-dilation, however, it could be done arbitrarily slowly and the clocks could be left in position arbitrarily long, so that the effect was negligible.— — Preceding unsigned comment added by MathewMunro (talkcontribs) 14:26, 22 March 2020 (UTC)
I'm sorry if I misunderstood you, but I assumed your use of "ideally" indicated that that aspect was not essential. I can assure you that the physicists who conducted experiments verifying time dilation in which kinematic and gravitational time dilation were both significant, such as the Hafele–Keating experiment and Gravity Probe A, took both into account; if the theory was erroneously based on gravitational potential, that would have come out – as it would have by the correction applied for GPS satellites not working properly.  --Lambiam 16:32, 22 March 2020 (UTC)
Regarding "Gravity Probe A" - clearly, a space-based measurement of time-dilation can not settle whether or not time-dilation is less or more underground than on the surface of the Earth!MathewMunro (talk) 01:48, 23 March 2020 (UTC)
It seems relative density becomes a factor ("The young centre of the Earth") and a estimate by Feynman of younger by "a couple days" was quite a bit off. fiveby(zero) 17:00, 22 March 2020 (UTC)
A preliminary scan of "The young centre of the Earth" paper suggests that it was a purely calculational paper, not supported by any measurements of time-dilation deep underground. They used the phrase "proof by ethos" to explain why the great Richard Feynman's gross mis-estimation was not picked-up for decades - well I suggest that the rejection of my criticism and my suggested way of experimentally testing it has been rejected by Wikipedians due to my lack of ethos! — Preceding unsigned comment added by MathewMunro (talkcontribs) 23:55, 22 March 2020 (UTC)
I really have no idea, but found a neat graph showing acceleration due to gravity is actually larger within the mantle. equivalence principle and the integration ${\displaystyle T_{d}(h)=\exp \left[{\frac {1}{c^{2}}}\int _{0}^{h}g(h')dh'\right]}$ in Gravitational_time_dilation#Definition may help. ${\displaystyle g(h')}$ is the g-force. fiveby(zero) 16:19, 23 March 2020 (UTC)
This graph shows that (in the model used to compute it) there is a discontinuity in the density at the boundary between the core and the mantle. The section title "Definition" in the article is IMO a misnomer. A theoretical formula cannot be the definition of something that can be measured in an experiment. This is like calling using Kepler's Third Law formula ${\displaystyle T={\frac {2\pi }{\sqrt {GM}}}r^{3/2}}$ a definition of "orbital period". In fact, the article is in want of a definition.  --Lambiam 17:51, 23 March 2020 (UTC)
That's an interesting model of Earth's gravity below the surface, however it's in conflict with the observation that the gravity at the bottom of the Mariana Trench is 99.83% as strong as it is at the surface - MathewMunro (talk) 00:12, 24 March 2020 (UTC)
Earth is lumpy. fiveby(zero) 01:12, 24 March 2020 (UTC)
"As you go down below the Earth's surface, in a mine shaft for example, the force of gravity lessens." - Dr Nicole Bell, Chief Investigator at the ARC Centre of Excellence for Particle Physics at the Terascale (CoEPP), and School of Physics at The University of Melbourne. Source https://www.abc.net.au/science/articles/2012/11/21/3636714.htm - they may have been wrong, but regardless, underground time-flow-rate measurements, combined with gravity measurements, combined with those same measurements made an equal distance from the Earth's axis at a different gravity could be used to both isolate general-relativity/gravitational time-dilation, and to provide experimental verification or rejection of the theory that time dilation is a function of distance from the centre of a massive object rather than being a function of the strength of gravity. MathewMunro (talk) 05:53, 24 March 2020 (UTC)
My understanding is that the relative time dilation between two locations is not a function of distance from the center of a massive object. It is a function of the "strength of gravity", but you'll need someone with a physics background to explain properly and correctly. Was hoping "The Young Centre of the Earth" and the graph of gravitational acceleration would lead to a good explanation. It seems you may be making a mistake in thinking about time dilation at a location (time-dilation at the centre of the Earth would be zero), it's time dilation relative to a reference location. When the time dilation of GPS sattelites are discussed it's relative to the surface of the Earth, not the center of the Earth. You can simplify for sattelites using the classical shell theorem and law of universal gravitation to make it look like a "function of distance from the centre", but as "The Young Centre of the Earth" shows and you correctly point out, that simplification does not hold when a location is beneath the surface of the Earth. fiveby(zero) 13:22, 24 March 2020 (UTC)
Time runs faster in orbit where gravity is lower. Logic would dictate that it also runs faster at the centre of the Earth, but that is not current dogma, ever since Feynman declared that the Earth's core would be a few seconds younger than the surface. It also has not been experimentally verified by checking the rate clocks run at underground near the equator compared to how fast they run on the surface further from the equator, an equal distance from the Earth's axis. MathewMunro (talk) 00:46, 25 March 2020 (UTC)
Is that because of gravity, or because of speed relative to earth? ←Baseball Bugs What's up, Doc? carrots→ 01:44, 25 March 2020 (UTC)
I shouldn't have introduced orbital objects, as I've just opened another can of worms :) There are special relativity effects, however below a certain orbit level somewhat higher than the orbit of the moon, objects in orbit will be travelling faster than they do on the surface of the Earth at the equator, which would only slow down the rate that time passes for them even more according to current scientific consensus. "Does time go faster at the top of a building compared to the bottom? - Yes, time goes faster the farther away you are from the earth's surface compared to the time on the surface of the earth. This effect is known as "gravitational time dilation"..." - Assistant Professor of Physics at West Texas A&M University. Source: https://wtamu.edu/~cbaird/sq/2013/06/24/does-time-go-faster-at-the-top-of-a-building-compared-to-the-bottom/ MathewMunro (talk) 04:24, 25 March 2020 (UTC)
I was expecting to see the elevator and rocket ship passing by clocks explanation similar to this. Also thought using the term 'g-force' instead of acceleration was confusing when talking equivalence principle. Anyway, integrate the acceleration of the rocket ship over the distance between clocks to find relative velocity and how much slower the clock is running (special relativity), integrate the acceleration due to gravity in free fall and general relativity tells you there is no difference is my limited understanding. I did not see the word 'acceleration' in any of the responses The graph is from Preliminary reference Earth model, here's the source From a practical viewpoint, such a modular construction is very convenien. It is much easier to perturb a particular feature of a model when it is separated from the remaining ones by clearly defined discontinuities than to alter a model that by definition is continuous.. Thought the graph was illustrative, but i am sure they could do better this century vs. 1981. fiveby(zero) 18:54, 23 March 2020 (UTC)
MathewMunro, do you have a source for that observation? The only obviously related thing that crops up in search results for Mariana Trench and 99.83% is this also calculational (and pretty dubious) discussion on Reddit. 89.172.17.213 (talk) 04:39, 24 March 2020 (UTC)
You're right, it was an estimation, by a reddit user, based on an incorrect assumption of uniform density. Gravity likely does increase a tiny bit going down a mine shaft vs the gravity immediately above, however, unless there are some pretty exceptional local density anomolies, the gravity at the bottom of a deep mineshaft anywhere near the tropics would be less than the gravity on the surface at an equal distance from the Earth's axis, further from the equator, (due to the distance from the centre of the Earth being less than it is at the surface of the mine shaft - due to the Earth's bulge at the equator, and due to the fact that in the mine shaft, some of the Earth's mass is acting against the gravity from the Earth's centre of mass), and so it would still be a great way to detect gravity-based time-dilation without any differences being due to special relativity, and it would also either confirm or refute the young centre of the Earth theory. MathewMunro (talk) 06:55, 24 March 2020 (UTC)

## Why in normal there are amylase and lipase in blood?

Amylase and lipase are enzymes that considered exocrinic (rather than endocrinic). My question is why do we see them in blood (they have a normal range there) while they should allegedly to be in the GI only as exocrinic. I didn't find the explanation for their presence in blood as exocrine enzymes. ThePupil (talk) 00:20, 22 March 2020 (UTC)

High amylase levels in blood plasma are associated with trauma to the glands producing amylase. Apparently, a (very) low level of leakage is normal. As to the lipases, lipoprotein lipase is supposed to function in the bloodstream, where it hydrolyzes triglycerides into fatty acids for cell consumption, and hepatic lipase can function in the bloodstream to keep HDL inactive. Rather than "exocrine", the term "paracrine" may be more appropriate for glandular excretions that are internal but not endocrine.  --Lambiam 04:00, 22 March 2020 (UTC)
Thank you. In all normal health people there is a level of amylase. What's its function in the blood? (I'm not asking about pathological levels of it, but about its presence in healthy people and its function then). You explained well the function of lipase in healthy people, thank you! ThePupil (talk) 13:29, 22 March 2020 (UTC)
Don't take my word for it as I'm not an expert, but my understanding is that its presence, although normal (abnormally low levels may also indicate morbidity), is accidental rather than functional, as I attemped to suggest above by using the term "leakage". Once in the blood, amylase also breaks down polysaccharides in the blood serum, but that is not a significant thing. This source states explicitly that pancreatic amylase enters the blood through "an unknown pathway", but Chempedia states that amylase enters the blood largely via the lymphatics. That may also hold for salivary amylase.  --Lambiam 15:51, 22 March 2020 (UTC)

# March 23

## Wet Sciences Books That Would Be Good For A Mathematician

I was not sure how to phrase the title. I was a mathematician, but I left academia due to mental illness. I've always been fascinated by the "wet sciences", biology and medicine, in particular the immune system and viruses. While I can read a medical journal paper reasonably enough (research is reasearch), I don't really feel like I "get" these fields. With math, everything makes sense to me, it's abstract and clearly defined. Medical science, and related fields, on the other hand, seem like a pile of data that sort of fits together. I'm sure that is a defect in how I think and not the science, but I'd like to understand it better. So, I'm not looking for sources that cover the mathematics of these fields, but sources that would fit well with how a mathematician thinks - more abstract and deductive, if possible (physics has approaches like this, it feels like other sciences could). It doesn't need to be an advanced book, even intro stuff with this approach would be helpful. Thank you for the long read and any answers24.3.61.185 (talk) 11:35, 23 March 2020 (UTC)

During this interesting week, I had a little extra reading-time on hand, so I pulled an old book off my shelf - one that was gifted to me by my great friend, who is a clinician and an epidemiologist; and who, though trained as a physician in the United States, chooses to practice medicine overseas. The book is Complications: A Surgeon's Notes on an Imperfect Science. The presentation is not that of a textbook; but that may be the whole point - you have to adapt your way of thinking to fit the problems and solutions of a totally different discipline. Nimur (talk) 14:09, 23 March 2020 (UTC)
You might like to try "The Beautiful Cure: Harnessing Your Body’s Natural Defences".--Phil Holmes (talk) 14:52, 23 March 2020 (UTC)
If you consider neurology a wet science (after all it deals with wetware), I have found the writings of Oliver Sachs on neurological topics pleasantly perspicaceous. For sociobiology, perhaps enough of a biological topic to be on the wet side of life, try E. O. Wilson. I read Molecular Biology of the Gene by James Watson a long, long time ago; while I did not get everything, I thought it was an eye opener. I did not read his Molecular Biology of the Cell (not to be confused with the journal of that title), but on Amazon the current (7th) edition has 4.2 out of 5 stars, which is very high for a textbook. The 4th edition is freely available online, so you can get an idea before buying anything. Or perhaps it is already good enough; you're not studying to become a cell biologist.  --Lambiam 15:49, 23 March 2020 (UTC)
Lots of biology makes more logical sense if you take an evolutionary perspective; that can help to place all the diversity of facts. I would recommend firstly Richard Dawkins The Selfish Gene. And, taking the message to medicine, try Nesse & Williams Evolution and Healing: The New Science of Darwinian Medicine, which I think is the same book as that with the title Why We Get Sick. Subsequent research has refined some of the details, but the principles hold true, and both books are beautifully and accessibly written. Jmchutchinson (talk) 20:30, 23 March 2020 (UTC)
We have an article (ok, redirect), mathematical biology. Added: In case this gives inspiration, Eric Lander, of human genome fame, started out as a research mathematician. 2601:648:8202:96B0:386A:A40C:EBB1:ACC0 (talk) 20:33, 23 March 2020 (UTC)
• Speaking as a (neuro)biologist), I'm afraid trying to find mathematical rigour in something like biology is going to be futile effort. It not at all a defect in how you think, it's what the field is like. Our understanding is incomplete and basically empirical. There are no absolute certainties or proofs. I rather like that myself, but I can see how I can drive someone with a mathematical background mad. Having said that, Molecular Biology of the Cell as suggested above is a fantastic textbook, but probably too in depth for what you're after. Fgf10 (talk) 09:30, 24 March 2020 (UTC)

## Viral lethality and evolution

From an evolutuionary view, is it disadvantageous for a virus to be highly lethal because the host's death prevents the virus' further spread (so that the natural selection selects those with low lethality to keep hosts alive)? Thanks. 212.180.235.46 (talk) 13:38, 23 March 2020 (UTC)

Isn't it amazing that with the power of the internet, we have near-immediate access to almost the whole of human knowledge - and equally amazing that for almost any interesting question, there is a high-degree of certainty that somebody in the scientific community has addressed it in great detail? In other words, if there is a meaningful question, there is a sort of ...pressure on a large number of professional researchers to try and answer it... and over the long run, one of them probably has answered it. These insights may help you to understand the nature of populations and selection pressure: there are no short-term guarantees, only long-term probabilities...
Here is the astonishingly relevant Evolutionary Insights into the Ecology of Coronaviruses (2007).
In case this is a little bit dense, let me try to summarize it in one sentence: on the scale of decades, virus evolution seems to be pretty random, and a lot less governed by selection-pressure - so while "survival of the fittest" makes for a very nice teachable sound-bite, the reality is much closer to "survival by a completely random bunch of 'em, with no specific identifiable benefit." "Natural selection" surely exists over the very long-term; but that ugly random-streak shows up in evolution and population-ecology way more often than they usually teach in high-school biology!
For further reading, the concept of a "reservoir population" of asymptomatic virus infestation is discussed here: Identifying reservoirs of infection: a conceptual and practical challenge (2002). It seems that this idea of a stable population of harmless viruses - "nonpathogenic... infections in reservoir hosts..." - well, this idea is conceptually pleasing but it's actually difficult to show in practice with any degree of convincing evidence.
Nimur (talk) 14:21, 23 March 2020 (UTC)
That's maybe a bit of a strong assertion, depending on what exactly is meant by the OP's question. Certainly much bacterial material is healthfully incorporated into our bodies, both at the level of mitochondria and gut flora. In the case of the gut flora, some of the little beasties involved are definitely infectious or harmful in other areas of the body but otherwise playing well with us. Matt Deres (talk) 17:48, 23 March 2020 (UTC)
It's worth remembering that evolution doesn't have an "end goal" in sight, and isn't trying to reach some future goal. It's a process acting only on current conditions, i.e. if I survive long enough to reproduce this generation, I reproduced during this generation. So, let's look at a highly lethal one, like Ebola. Ebola is transmitted best through contact with bodily fluids, so evolution may then favor something that increases that contact. A haemorrhagic fever works great for that, as you start bleeding out of every orifice, and then some, meaning there is a lot more opportunity for bodily fluid contact than would otherwise be the norm. So, it transmits to new hosts much more easily. A side effect of this is that it is highly lethal, since bleeding out of everywhere tends to kill you quickly. That means Ebola outbreaks tend to burn themselves out quickly, running out of hosts. Ebola will never be as globally successful as something with a far lower mortality, like influenza or SARS-CoV-2, but within its local population and region, it has a highly effective method of reproduction and transmission to new hosts. As long as it also has some sort of reservoir between outbreaks, be that zoonotic, or some sort of surface or buried material (think spores, like anthrax, but something with a virus), it will continue to exist and occasionally crop up. --OuroborosCobra (talk) 14:38, 24 March 2020 (UTC)
Selection works only on variants whose advantages or desadvantages are large. If they are not large they are indifferent and the variant frequency will drift. It is possible that the advantage in making the host very sick is large: so e.g. plague spreads best if the bacterial load of blood is large so that fleas have a larger chance of picking up some yersinia with a blood meal. That this large blood load will kill the patient is secondary, as long as large numbers of fleas are freshly infected before the patient dies. As Cobra says, an intermediate/reservoir host helps, but killing the patient ist really a desadvantage only if you kill them before they can reach you to the next victim. Ebola outbreaks ended quickly more because the symptoms were so serious that the patients were quickly insulated and less because the virus ran out of hosts, that is, they ran out of hosts because of the insulation. Without insulation measures any epidemic can destroy large populations, as did smallpox for Native Americans. 89.204.130.58 (talk) 16:50, 25 March 2020 (UTC) Marco PB
Yup. Bubonic Plague is actually a terrific example for this in another way as well. It kills its intermediate reservoir/host even more than it does us. It builds up a biofilm in the flea gut that eventually blocks up the gut completely, preventing it from digesting material. The flea, out of starvation, will try to feed again, which only results in regurgitation of bacteria into a new host, infecting them. The flea will eventually die from starvation. Bubonic plague literally kills its primary transmission vector, but as long as it only kills it after infecting at least one host, the bacteria will have successfully spread. Then, multiple uninfected fleas feed on the new host, and the cycle repeats, now able to spread to multiple new victims. --OuroborosCobra (talk) 15:22, 26 March 2020 (UTC)
See optimal virulence. --47.146.63.87 (talk) 19:05, 25 March 2020 (UTC)

## Newbie audio panning

I have an MP3. The stereo is actually two mono channels, recorded via breakout adapter. I need to pan the two mono channels, 25-75 and 75-25. I'm on Linux. I'd prefer a command-line, or script solution. Thanks! — Preceding unsigned comment added by 182.156.108.31 (talk) 15:56, 23 March 2020 (UTC)

You can do that with ffmpeg but be ready to spend a month or two puzzling over the man page. The trac wiki (trac.ffmpeg.org) is very helpful in figuring out stuff like that. 2601:648:8202:96B0:386A:A40C:EBB1:ACC0 (talk) 20:50, 23 March 2020 (UTC)

# March 25

## Was Toxic Oil Syndrome really caused by cooking oil?

Hi Wikipedia, I've been looking into the topic of Toxic oil syndrome and when I went into the Spanish Wikipedia article, it had a rather lengthy section on conspiracy theories, namely one claiming that it hadn't been caused by cooking oil, but a tomato pesticide instead. Checking the three sources cited, they all seemed to be from conspiracy blogs that didn't seem very trustworthy, so I decided to be bold and delete the section. However, I recently began looking at online resources in English and I found this [8] article. In fact, it is mentioned in a similar section in the English article. This source made almost all of the claims that the Spanish article made, and it seems to be a reliable source, unlike the blogs cited in the Spanish article. A talk page discussion was opened on it long ago but it didn't lead anywhere. I'm a bit conflicted. Of course, I'm not very keen on believing conspiracies, but this does seem to have a reliable source. Meanwhile, the official version still is that the oil was at fault. Can anyone more familiar with this topic shed a bit of light? GoodCrossing (talk) 00:20, 25 March 2020 (UTC)

I remember that time, and the cause was then stated to be a charge of cheap edible oil mixed with gun oil, specifically oil for machine guns. Gun oils do often contain additives such as Polytetrafluorethylene (PTFE) or Molybdenum, which are directly or indirectly toxic and/or neurotoxic. But if you have a source we can mention this alternative organo-phosphates theory without necessarily backing it 89.204.130.58 (talk) 14:32, 25 March 2020 (UTC) Marco PB
I am familiar with the event as I'm from Spain. However, the only reliable source I can find is that Guardian article, and it seems to be largely based on the original work of Dr. Muro, who seems to lead the conspiracy theory. I haven't found any other scientific consensus on if Muro's theories are correct or not. GoodCrossing (talk) 15:45, 25 March 2020 (UTC)
Two brief contemporaneous articles from the New Scientist about the ongoing trial: [9], [10]. The theory of pesticide poisoning came first; the theory of an organized cover-up came only later, but our article strongly suggests they are one and the same thing. Our article also does not cover the trial; I think it should.  --Lambiam 21:04, 25 March 2020 (UTC)
Here is an earlier New Scientist article on the debate about the cause. It mentions the alternative theory that toxic organophosphates were the culprit without hinting at a conspiracy.  --Lambiam 21:15, 25 March 2020 (UTC)

## Likelihood of recovery from a serious case of COVID-19 with medical assistance

In general, what is the likelihood that a person who develops a serious (potentially life-threatening) case of COVID-19 will recover if they receive medical attention? Freeknowledgecreator (talk) 01:49, 25 March 2020 (UTC)

In the initial stages, all cases are potentially life-threatening. For any meaningful statistics, one needs an operational objective definition of "serious" that is applied across the board. Did the patient already receive the best medical care, given the state of medical knowledge and technology as soon as they became symptomatic, or did treatment only commence after the disease progressed to a serious condition? And what constitutes recovery? Not dying is not the same as recovering. Little is known yet about long-term damage. So the mortality risk, even if known, will not tell us the answer. It may be possible to dredge up some figure from the slush of data, but in this stage I wouldn’t attach much meaning to it.  --Lambiam 03:46, 25 March 2020 (UTC)
You understand what I'm asking. What are the chances that medical science can save someone who looks likely to die of COVID-19 if they don't get help? Freeknowledgecreator (talk) 04:45, 25 March 2020 (UTC)
Your response is much more indignant than mine. I'm not asking for a precise answer to the question how likely it is that someone who looks likely to die of COVID-19 can be saved by medical science; an answer in general terms is fine. Qualify that answer for different kinds of patients as much as you wish. Freeknowledgecreator (talk) 22:50, 25 March 2020 (UTC)
It is better not to comment than to make rude or hostile comments, such as the above. I would have thought that the meaning of the expression "general terms" did not require explanation. I am simply asking whether most people who look likely to die of COVID-19 can be saved by medical assistance. The question is perfectly clear. It remains clear regardless of the fact that different kinds of patients may be more or less likely to die. Freeknowledgecreator (talk) 23:47, 26 March 2020 (UTC)
In "general terms", this thing is quite new, and we don't have enough information to answer the question. ←Baseball Bugs What's up, Doc? carrots→ 23:49, 26 March 2020 (UTC)
Thank you. A "no one can answer the question because there isn't enough information available" response is perfectly appropriate. Certainly better than rude outbursts. Freeknowledgecreator (talk) 23:52, 26 March 2020 (UTC)
Which is why I ignored your question entirely, until someone said "we can't answer it because we don't know what 'serious' means," and you responded by indignantly saying "you understand what I am asking." No. We don't. We don't know what "serious" means. We don't know what "general terms" means. I explained to you why, but I ignored your initial question as it was not answerable. I explained to you in plain terms what we needed from you in order to answer it, and you did not provide. --OuroborosCobra (talk) 19:42, 27 March 2020 (UTC)
If you felt that my initial question was unclear you could have politely asked me to clarify it instead of responding with rude outbursts such as the above. Freeknowledgecreator (talk) 01:35, 28 March 2020 (UTC)

## Possible effects of many people self-isolating on Wkipedia editing etc

Greetings all in these 'interesting times'

I was wondering, what the potential effects of millions (billions?) of possibly very bored people having to stay away from, school, work etc on Wikipedia?

Will we have many new useful editors, or will we have so much vandalism or good-faith bad editing that we can't cope with it?

If this has already been covered, please direct me there. Regards, 220 of Borg 04:14, 25 March 2020 (UTC)

220 of Borg, there's a related discussion at User_talk:Jimbo_Wales#Create_a_silver_lining. I happen to be currently re-watching TNG ;-) Gråbergs Gråa Sång (talk) 08:03, 25 March 2020 (UTC)
Not streaming it, I hope! 😲 Thanks, I'll have a look at that thread. 👍 220 of Borg 09:01, 25 March 2020 (UTC)
In the area of self-isolated pastimes, I was told that Pornhub offers a week free premium. Gråbergs Gråa Sång (talk) 09:05, 25 March 2020 (UTC)
I think it is more like a month, at least in Spain, Italy and France. [11]. Well, getting back to topic, I think many more people will edit, and not in bad faith, and many older non-active editors may come back to stay for a while longer, I trust that this time will be benefitial for Wikipedia. Apolo234 (talk) 09:25, 26 March 2020 (UTC)

## Blood & gender

If you take a blood sample from a random person, is it possible to tell whether the sample came from a male or female, purely from this sample? 92.9.144.104 (talk) 04:52, 25 March 2020 (UTC)

Yes. Looking for the presence vs absence of the Y chromosome is one way. doi:10.1016/0379-0738(86)90166-0 Analyzing blood and other fluid residues at a crime scene is a pretty important task in forensic science, which includes methods like serology and a boatload of other techniques. DMacks (talk)|
Convenience link: Y chromosome. Regarding the section title, note that today a sex-gender distinction is increasingly accepted. This is particularly notable in this context because an assumption based on karyotype will sometimes be wrong. Intersex people may have a phenotype that one would not typically associate with their genotype. People with complete androgen insensitivity syndrome have an XY genotype but a female phenotype. Some people have X0 (X-naught) or XXY genotypes, or an XY genotype but a dysfunctional SRY gene or other Y chromosome abnormalities and therefore not a typical male phenotype. --47.146.63.87 (talk) 06:01, 25 March 2020 (UTC)
If I'm reading Red blood cell correctly, red cells lack DNA. ←Baseball Bugs What's up, Doc? carrots→ 08:27, 25 March 2020 (UTC)
Red blood cells have a nucleus that contains DNA while they are within the bone marrow. When they move from the bone marrow to the circulation, that nucleus and the DNA contained within it are extracted and discarded, so that circulating RBCs ordinarily contain no nuclear DNA. However, there are occasional circulating RBC's where this process has failed. This results in circulating nucleated red blood cells (NRBCs). They are normal in neonatal blood, but should be very rare in circulating adult blood and their presence would prompt a search for a disease process that might be responsible for them. -Nunh-huh 01:42, 26 March 2020 (UTC)
Turns out we have a whole Nucleated red blood cell article:) DMacks (talk) 04:51, 26 March 2020 (UTC)
Yes, but blood also contains White blood cells, which do contain a nucleus with DNA.-gadfium 08:34, 25 March 2020 (UTC)
A useful microscopic finding would be the finding of Barr bodies within certain neutrophils on a peripheral smear, which would imply the blood was from a female. -Nunh-huh 01:42, 26 March 2020 (UTC)
Good point (and complementary positive test to presence of Y-chromosome). One could also look for various horomone levels (Prostate-specific antigen for males, multiple options for females). DMacks (talk) 04:51, 26 March 2020 (UTC)
And some people with a bone marrow transplant from a person of a different sex can show up with different sex to the rest of the body (chimera). Graeme Bartlett (talk) 09:59, 25 March 2020 (UTC)
So this Y chromosome, is found in white blood cells, and red blood cells within the bone marrow for the most part? 67.175.224.138 (talk) 04:42, 26 March 2020 (UTC).
The Y chromosome is found in every normal cell nucleus of a male human (and other mammals). Most human (etc.) cells have one nucleus; a few specialised cells have multiple nuclei; however red blood cells, aka Erythrocytes are unusual because they do not have nuclei, so do not contain any chromosomes. During the process by which red blood cells are formed in bone marrow, the developing cells which will become red blood cells expel their nuclei to become reticulocytes, which are released into the bloodstream and which mature into erythrocytes in a day or two (as compared to their overall lifetime of 3 to 4 months). {The poster formerly known as 87.81.230.195} 90.197.27.39 (talk) 11:33, 27 March 2020 (UTC)
Elaboration/nitpick: "normal cell" here means "nucleate somatic cell". Note that platelets, found in blood, are cell fragments rather than complete cells. --47.146.63.87 (talk) 19:41, 27 March 2020 (UTC)

What is the motivation for the migration of anadromous fish like salmon? It seems to me awfully inefficient to have a fish live in the sea but also be able to adapt to fresh water just to go spawn somewhere and have a good chance of ending up in a bear's stomach along the way. What is the evolutionary advantage that helps the fish which perform this migration? The fish migration article wasn't of much help. 89.172.17.9 (talk) 12:15, 25 March 2020 (UTC)

One possibility is: living in the open sea many more adult salmons can find much more food than they would in some small mountain brook. On the other hand their hatchings are subject to much less predation in small mountain brooks than they were in the ocean. The most dangerous potential predators there being their own parents, and they die very conveniently just after having laid their eggs; also incidentally increasing the local disponibility of food. 89.204.130.58 (talk) 14:50, 25 March 2020 (UTC) Marco PB
Some support for this theory can be found in the article "The evolutionary origins of diadromy inferred from a time-calibrated phylogeny for Clupeiformes (herring and allies)". It mentions "evidence that temperate anadromous fishes are derived from freshwater ancestors that began migrating to oceans to exploit the higher productivity". But they conclude, "[o]ur results [for a different fish order than the salmons and allies. --L.] do not support the productivity hypothesis". Also, "the evolutionary origins of diadromy remain poorly understood". Evolution may take a warped path. Sharks started as sea fish, but some families became freshwater fish and so developed (like us mammals) a way to keep their blood as salty as sea water, rather than developing a physiology supported by "sweet blood", and then migrated out to the see again – and rather than reverting the previous adaptation, evolved desalination, so now the sea water first gets desalinated and then again salinated to become blood. Or so I have read somewhere. Next to the fitness advantage of diminished risk of predation for the young brood mentioned by Marco PB, it is conceivable evolution randomly followed the path of the spawners returning to freshwater for brood not adapted to sea water, instead of the alternative of the brood adapting to survive a salty environment.  --Lambiam 20:05, 25 March 2020 (UTC)
Yes, evolution is path-dependent. It's a "blind watchmaker" that can only work with what it's got. Based on what you cited, salmon are descended from freshwater ancestors that started moving into more saline environments. But the juveniles retained the adaptation to freshwater, and so the adults have to return to that to spawn. This is similar to amphibians, where eggs and juveniles usually require an aquatic environment. As long as a trait is "good enough", it won't be driven out of a species by natural selection. The myriad examples of poor design in organisms are testament to that. --47.146.63.87 (talk) 21:52, 25 March 2020 (UTC)

## How is a virus in my eye a danger?

As a new SARS virus can be transferred on hands, health services advise people to avoid touching their mouth, nose and eyes. Why eyes?
I understand how a virus, which attacks the mucous membrane of the respiratory system, can get there through mouth or nose. What I don't get, however, is: how can a virus move from eyes to a throat and further down to lungs? --CiaPan (talk) 17:45, 25 March 2020 (UTC)

• Tear ducts perhaps? Bazza (talk) 18:28, 25 March 2020 (UTC)
• Eyes are naturally wet. Assume that any part of the body which is naturally wet represents an entry point.
In this case, it's more specifically the tear ducts. The eye's natural dust flushing mechanism runs throughout the day (and at night, although often a little less). Tears (so small you don't notice) from the lacrimal glands flush the surface of the eye and are carried away (dust and virus too) down the nasolacrimal duct and into the sinuses (hollow spaces) of the nose. Obviously that then connects to the throat and trachea, and into the lungs. From there on its virus party time. Andy Dingley (talk) 18:29, 25 March 2020 (UTC)
Thank you, Bazza and Andy Dingley.This makes the official advices pretty reasonable. I just can't believe I never learned about it! Thanks again. --CiaPan (talk) 19:44, 25 March 2020 (UTC)
This is why your nose runs when you cry. --47.146.63.87 (talk) 20:27, 25 March 2020 (UTC)
Yes, I know those happen together - but my nose usually runs when I do not cry (maybe because I almost never cry), so the causal relation is not that obvious; running nose and tears might be independently caused by the same neural signal. Now when I know about the tear duct, the correlation is more obvious - but it did not seem so definite to me before to make me deduce the existence of the duct myself. CiaPan (talk) 21:42, 25 March 2020 (UTC)
The proof is this unpleasant YouTube clip of a boy crying milk (don't try that at home folks). Alansplodge (talk) 12:30, 26 March 2020 (UTC)
Better to be known as the boy who cried milk than as the boy who cried wolf.  --Lambiam 11:44, 28 March 2020 (UTC)

# March 26

## Other blood groups (A, B, AB) can have only once donation from group O?

Group O in blood is a universal donor. Is it correct that it's possible for other blood groups people to get this blood only once at life? I was told so today and I'm not sure if it's a myth or truth.ThePupil (talk) 00:26, 26 March 2020 (UTC)

No, what you were told is incorrect. A person with AB, A, or B type blood can receive more than one transfusion of blood type O if necessary. - Nunh-huh 01:35, 26 March 2020 (UTC)
And in general it's O-negative that's the universal donor.[12]Baseball Bugs What's up, Doc? carrots→ 04:38, 26 March 2020 (UTC)
Article: ABO blood group system. If someone hasn't been exposed to non-self ABO antigens, they won't have antibodies against them, and hence won't have an adverse reaction on initial exposure. (This is just like immunity to a pathogen. It's the same mechanism.) But this is not guaranteed because people can become exposed without knowing it. A frequent cause is during pregnancy and childbirth; it's fairly common for some cells to leak across the placenta. If this happens, and the mother and fetus have different blood types, the fetus will be sensitized to the mother's ABO antigen(s). So intentionally infusing non-compatible blood is not done except as an absolute last resort. This same placental leakage, going the other way, is what causes Rh sensitization in mothers. --47.146.63.87 (talk) 07:23, 26 March 2020 (UTC)
In general, even people who have never been exposed to blood products are already sensitized to ABO antigens. These are naturally occurring antibodies. In general, people with healthy immune systems are expected to present with naturally occurring ABO antibodies appropriate for their ABO type. [13] [14]
This is not simply the result of intrauterine exposure to a discordant mother's blood. A type O child of a type O mother will have anti-A and anti-B antibodies, even though there is no chance that they were exposed to antigens from the mother in utero (since she doesn't have those antigens). The antibodies are thought to be the result of encountering ABO blood group antigens (or antigens that cross-react with them) in foods or microorganisms. "Sugars that are identical to, or very similar to, the ABO blood group antigens are found throughout nature." [15] Another theory is that "these antibodies are genetically coded to be produced even though the body has never been exposed to that antigen before." [16] - Nunh-huh 07:36, 26 March 2020 (UTC)

# March 27

## Communicability

Given the current pandemic, we've been hearing a lot about mortality rates for diseases, but I'd be interested in learning more about relative communicability rates. We have a couple of articles that touch on the topic, such as Infection and Transmission (medicine), but I'm not seeing much that lists objective values. Our article on measles asserts (with a reference and I've seen it confirmed elsewhere) that it is the most easily communicable disease known. Assuming that's true, what would be the top ten or twenty? Given that diseases can travel in wildly different vectors where is a bit of apples to oranges in this, but it seems like there has been some work in determining how many individual germ agents are needed to induce infection in a person with a normal immune system. Do we have that somewhere? Matt Deres (talk) 13:32, 27 March 2020 (UTC)

Basic reproduction number may somewhat address this issue. If by "germ agents" you mean the infectious microorganisms (bacteria, viroids), their invidual infectiousness varies wildly and does not correlate in any obvious way with transmission rates.  --Lambiam 17:22, 27 March 2020 (UTC)
You might find the Microbe-scope illuminating.--Phil Holmes (talk) 10:26, 28 March 2020 (UTC)

# March 28

## Coronavirus spike

Coronavirus cases

Why the spike in China on February 17th? Some sort of new test? And do we believe they had essentially no new cases in March? --Guy Macon (talk) 12:58, 28 March 2020 (UTC)

They changed their diagnostic criteria (here, here, or here). Fgf10 (talk) 13:33, 28 March 2020 (UTC)