Wikipedia:Reference desk/Archives/Science/2020 July 8

= July 8 =

The colour of the sea
I was told the colour of the sea (blue/green) 'is not really' colourful, and the reason we see it colourful it's because of the light waves. Then my question why these light waves don't work when we take from the same water a glass of water and hold it in our hands? --ThePupil (talk) 00:08, 8 July 2020 (UTC)
 * https://www.scientificamerican.com/article/why-does-the-ocean-appear/
 * A single glass does not contain enough water to absorb very much light. --Khajidha (talk) 02:14, 8 July 2020 (UTC)
 * Quite so. Consider as a parallel, ThePupil, that an empty, clear glass (or plastic) container also does not appear blue, even though the sky (i.e. the atmosphere en masse) does.[ citation not required ] {The poster formerly known as 87.81.230.195} 2.122.56.20 (talk) 12:11, 8 July 2020 (UTC)
 * That is a bit misleading though. Water is blue(-ish) because it absorbs non-blue wavelengths more for large enough bodies of water. The sky is blue, not because the atmosphere absorbs blue less than other wavelengths (or at least not in the most part), but because of Rayleigh scattering. See Diffuse sky radiation. Tigraan Click here to contact me 15:53, 8 July 2020 (UTC)


 * The only reason you see colour in anything is light waves. —Tamfang (talk) 02:25, 14 July 2020 (UTC)

Death of conjoined twins: does the second twin always simultaneously die, after the first twin dies?
I was reading about the recent case of conjoined twins, Ronnie and Donnie Galyon. This made me wonder: when you have conjoined twins, if one twin dies, is it also the case that the second twin "must" die, too? (At the same time, I mean.) Is it "theoretically" possible to separate previously "unseparatable" twins, when one dies? Seem like stupid questions, but I have no idea. Also, I guess that I am referring to conjoined twins that actually live for a bit ... not ones who die at birth or shortly thereafter. Thanks. Joseph A. Spadaro (talk) 03:36, 8 July 2020 (UTC)
 * Have you read Conjoined twins? {The poster formerly known as 87.81.230.195} 2.122.56.20 (talk) 12:17, 8 July 2020 (UTC)


 * Thanks. Yes, I had already read that prior to posting my question.  I don't see that it answers my questions.  Am I missing something in that link?   Thanks.   Joseph A. Spadaro (talk) 16:11, 8 July 2020 (UTC)


 * Does this article answer your questions? --Guy Macon (talk) 16:21, 8 July 2020 (UTC)


 * Ah, extremely interesting!  Thanks!   I am going to read that now!   Thank you.     Joseph A. Spadaro (talk) 20:46, 8 July 2020 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 20:17, 10 July 2020 (UTC)

Can a genuine FFP2 or KN95 respirator have earloops instead of headbands?
Thanks. Apokrif (talk) 11:43, 8 July 2020 (UTC)
 * As a person who has worn and been fit-tested for N95 respirators, if the tension in the earloops was strong enough to insure a tight fit, it would be too painful to wear. I don't know if there is a regulation that forbids earloops, but I can't imagine they would work. Jc3s5h (talk) 11:50, 8 July 2020 (UTC)


 * The specifications specify things like filter performance, flow rate, and pressure drop. You can design a mask any way you want to as long as it meets the specs.


 * This data sheet shows a KN95 with ear loops.


 * The reddit thread should be ignored, and instead you should look at the source, which is here: Note that NIOSH-42CFR84 only covers N95 masks. not FFP2 or KN95.


 * Any counterfeiter worth his salt will make the counterfeit look like the real thing. That CDC page really tells you how to identify mislabeled masks --which are a much bigger problem -- not counterfeit masks. It takes skill to make a counterfeit. Any idiot can slap a KN95 label on a non-KN95 mask they bought somewhere. --Guy Macon (talk) 13:40, 8 July 2020 (UTC)

covid-19 and personal possessions.....
I remember, back in 2014, hearing that the 2 Nurses in Dallas (Nina Pham and Amber Vinson) who contracted Ebola....had almost all of their possessions destroyed by the CDC for fear they might be contaminated by the Ebola virus. Has anything similar happened to Covid-19 patients? 67.253.78.55 (talk) 20:29, 8 July 2020 (UTC)
 * The viability of viral particles on surfaces differs greatly from virus to virus, just as whether a virus is best spread by body fluid contact or respiratory droplets. Comparisons between SARS-CoV-2 mitigation measures and those for Ebola virus or influenza virus may not be apt. --OuroborosCobra (talk) 21:13, 8 July 2020 (UTC)


 * May be so, though I recall hearing a few months back that SARS-CoV-2 could persist for up to at least 17 days on some surfaces...My question, however, is have any of the 3 million Americans who have had laboratory been ordered or encouraged to throw away their belongings?67.253.78.55 (talk) 21:49, 8 July 2020 (UTC)


 * That's still putting the cart before the horse. Is there any purpose at all in encouraging people to throw away their belongings? There was a lot of misreporting in the media early on about SARS-CoV-2 virus being detectable on surfaces days later, but these tests were not on viability. Detection of virus just means enough intact genetic material in the primer section used for RT-PCR existed for amplification and detection. It doesn't mean that there were intact viral particles viable for infection. There may not have been viral particles at all, just remaining genetic material. --OuroborosCobra (talk) 21:56, 8 July 2020 (UTC)


 * Perhaps I have not made my point clear, I am not advocating that SARS-Cov-2 positive patients should be required to discard their possessions for fear of contamination, rather, I am simply asking if this is the policy of public health agencies across the country.In late January when it started to become clear to me that a pandemic was inevitable I moved my many of my possessions (e.g. collections of magazines, photo albums, treasured childhood toys,important documents, books, etc) into plastic tubs and then into the attic lest I contract the virus and be ordered by local public health authorities ( I reside in the USA) to discard all of these items....I am now wondering whether this is a legitimate concern or if I can move these items out of the attic without fear that if I contract the virus I will be compelled to dispose of them. My concern about this was heightened by the fatc that in January it was reported that the Chinese Government was destroying cash in an attempt to curb transmission. 67.253.78.55 (talk) 23:35, 8 July 2020 (UTC)


 * ...All of which is stupid government overreaction. If you want to be 100% safe, quarantine the possessions for a week or two. You can speed this up with a UV disinfectant lamp. --Guy Macon (talk) 00:12, 9 July 2020 (UTC)
 * No US government agency is advocating destroying property, much less mandating it. If they were stupid enough to try, the courts would shoot them down on constitutional grounds ("The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated") and lack of scientific evidence (see below). You can take your stuff out of the tubs. --Guy Macon (talk) 00:08, 9 July 2020 (UTC)


 * Keep in mind that Ebola has a very high death rate compared to what we know so far about COVID-19. ←Baseball Bugs What's up, Doc? carrots→ 02:26, 9 July 2020 (UTC)


 * "I recall hearing a few months back that SARS-CoV-2 could persist for up to at least 17 days": IIRC I only heard until 3 or 7 (or 5?) days. Unfortunately, a quick googling doesn't return an English Wikipedia page addressing the issue (there should be one). Apokrif (talk) 09:32, 9 July 2020 (UTC)
 * "I recall hearing a few months back that SARS-CoV-2 could persist for up to at least 17 days": IIRC I only heard until 3 or 7 (or 5?) days. Unfortunately, a quick googling doesn't return an English Wikipedia page addressing the issue (there should be one). Apokrif (talk) 09:32, 9 July 2020 (UTC)

--Guy Macon (talk) 00:08, 9 July 2020 (UTC)
 * "The primary and most important mode of transmission for COVID-19 is through close contact from person-to-person. Based on data from lab studies on COVID-19 and what we know about similar respiratory diseases, it may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes, but this isn’t thought to be the main way the virus spreads." --CDC updates COVID-19 transmission webpage to clarify information about types of spread
 * "Coronavirus can last for long durations on different metal surfaces, ranging from hours to days.13, 14 Recent studies show that the coronavirus can last about three days on a plastic surface as well as on stainless steel surface, it can also sustain for a period of whole one day on cardboard, while it can only sustain only for about four hours on a copper surface." --Sustainability of Coronavirus on Different Surfaces
 * "The virus that causes coronavirus disease 2019 (COVID-19) is stable for several hours to days in aerosols and on surfaces, according to a new study from NIH, CDC, UCLA and Princeton University scientists published in the New England Journal of Medicine. The scientists found that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was detectable in aerosols for up to 3 hours, up to 4 hours on copper, up to 24 hours on cardboard and up to 2 to 3 days on plastic and stainless steel. The results provide key information about the stability of SARS-CoV-2, which causes COVID-19 disease" --New Coronavirus Stable for Hours on Surfaces


 * [Edit Conflict] The 17-days figure derives from a study widely reported, for example here.
 * The headline is (as so often with sensational journalism) misleading, since what was found was not viable viri, merely identifiable RNA traces. The actual study paper is here. {The poster formerly known as 87.81.230.195} 2.122.56.20 (talk) 15:01, 9 July 2020 (UTC)
 * Pedantic peeve point &mdash; the English plural of "virus" is "viruses" (though in this context you might better say "virions" or "virus particles").
 * In Latin, "virus" is a second-declension neuter noun ending in -us, the only one I've ever heard of, so it's not really clear what its regular plural would be (Latin Wiktionary says vira but I'm not sure how well-supported that is). Since it's a mass noun (roughly means "slime"), there's not a lot of call for a plural, and as far as I know none is attested (in Latin).  In any case viri already means "men".
 * Mea culpa. I assumed it to be first declension which, half a century after I was taught the language, is the only one I can still decline from memory. {The poster formerly known as 87.81.230.195} 2.122.58.253 (talk) —Preceding undated comment added 17:29, 10 July 2020 (UTC)
 * At least you didn't say "virii". That one really makes me itch. --Trovatore (talk) 21:33, 9 July 2020 (UTC)
 * What a shock. The popular press makes everything look as bad as possible. Who knew? :) --Guy Macon (talk) 16:10, 9 July 2020 (UTC)