Wikipedia:Reference desk/Archives/Science/2021 September 5

= September 5 =

How much of Speed of light can be decreased until Universe go unstable?
I feel stability of universe also depends on speed of light. So how much of Speed of light can be decreased until Universe go unstable? Rizosome (talk) 02:56, 5 September 2021 (UTC)
 * Where did you get this idea from? Also note that the speed of light varies depending on what it's traveling through. ←Baseball Bugs What's up, Doc? carrots→ 04:23, 5 September 2021 (UTC)


 * The metre is defined in the International System of Units (SI) as the distance travelled by light in vacuum in 1/299792458th of a second. It follows that the speed of light is exactly $299,792,458 metres per second$. If it goes down, this means that reciprocals have become unstable. --Lambiam 06:24, 5 September 2021 (UTC)
 * That's not a fact about the speed of light; it's a fact about how the meter is defined in SI. I think we have an article called variable speed of light; I haven't looked at it recently and don't know what it currently discusses, but you can't answer the question "what if the speed of light were lower" by talking about a particular system of units.  (It would certainly be fair to ask the questioner what is meant.) --Trovatore (talk) 16:19, 5 September 2021 (UTC)


 * Let's not some of us lose sight of the fact that the value c, colloquially referred to as "the speed of light," is a fundamental physical constant (we think) which light or other massless entities in a vacuuum necessarily must travel at, but that's an imposition on light by the universe, not something imposed on the universe by light. That light or other massless things travel at different velocities when not in a vacuum has no relevance to questions like Rhizome's.
 * As to that question, our article Fine-tuned universe may be of interest, as might Fine-tuning. {The poster formerly known as 87.81.230.195} 2.122.0.2 (talk) 19:36, 5 September 2021 (UTC)
 * Please read the section, and note this quote:
 * At first we might be tempted to think that a world in which the speed of light was slower would be a different world. But this would be a mistake. If c, h, and e were all changed so that the values they have in metric (or any other) units were different when we looked them up in our tables of physical constants, but the value of α remained the same, this new world would be observationally indistinguishable from our world.  The only thing that counts in the definition of worlds are the values of the dimensionless constants of Nature.
 * --Lambiam 21:56, 5 September 2021 (UTC)
 * But what if c alone were different, such that the value of α was also different? (I am asking on behalf of Rhizome, of course.) {The poster formerly known as 87.81.230.195} 90.209.121.112 (talk) 04:25, 6 September 2021 (UTC)
 * There is a shallow discussion at, although I wonder if the presentation correctly reflects the cited source. --Lambiam 07:26, 6 September 2021 (UTC)

Production of Chloroquine and Hydroxychloroquine
How are chloroquine and hydroxychloroquine produced by the pharmaceutical companies? Are they made semi-synthetically from the bark of the cinchona tree? Our articles on those medicines don't seem to say how they are manufactured or produced? (Maybe our articles should be expanded to include that information, as described in reliable sources, but this is the Reference Desk, not a content form.)

I am not asking whether they have value in treating or preventing covid. We know that they do not. I am only asking how these medicines are produced. Robert McClenon (talk) 21:07, 5 September 2021 (UTC)
 * In organic chemistry, you learn reactions are made through a series of steps involving SN2, SN1, E2, and E1. The trick is to know what the starting materials are. (I.e., fusing 2 benzene rings into 1.). Then, there's selecticity, i.e., adding a substituent in the ortho-, meta-, or para- position. 67.165.185.178 (talk) 03:32, 6 September 2021 (UTC).
 * The original source from cinchona was severely limited in World War II, when these compounds were first in demand as anti-malarials. Hence purely synthetic routes were developed. Articles from the time include this report from 1949 and this thesis. I'm not sure how large-scale manufacture takes place today and it is a shortcoming of the Wikipedia articles that this aspect is not covered. Mike Turnbull (talk) 11:13, 6 September 2021 (UTC)
 * I've now updated the chloroquine and hydroxychloroquine articles to add the chemistry in their history sections. Mike Turnbull (talk) 13:58, 7 September 2021 (UTC)
 * Chloroquine is a de novo synthesis; cinchona bark was never in the mix. You can reliably source possible syntheses but I don't think you could reliably source manufacturing process(es). UNIDO for example had to interpolate in 1985 ("step-by-step technical and economic details were not always available..."), and the ACS article above illustrates how a bench synthesis may have to be "translated" to manufacturing; that's the sort of detail I'd be surprised to see published. "Synthesis of Essential Drugs" has more detail on synthesis but probably fails WP:NOTTEXTBOOK. Yappy2bhere (talk) 21:45, 8 September 2021 (UTC)
 * Per MOS:CHEM It is our tradition to cite the first preparation of a compound. Most if not all commercially significant compounds are made by routes that are confidential to their manufacturers and may change according to the scale at which they are carried out. As said, many Wikipedia articles don't cover that. For chloroquine and hydroxychloroquine I added the routes from the 1940s which use 4,7-dichloroquinoline as an intermediate and I've now also written an article for that intermediate. My previous comment that The original source from cinchona was severely limited in World War II referred to using quinine directly as an antimalarial, not as a chemical intermediate: apologies for any confusion.  Mike Turnbull (talk) 11:38, 9 September 2021 (UTC)

Production of Ivermectin
How is ivermectin produced by the pharmaceutical companies? Is it produced by extraction and processing from the product of certain bacteria? (If so, are the bacteria soil scavengers that are producing the vermicides in order to compete with worms in scavenging the soil?) Our article sort of implies that, but only sort of implies that. (Maybe it should be expanded, but this is the Reference Desk.)

I am not asking whether ivermectin has value in treating or preventing covid. We that it does not. I am interested in the origin of the nonsense belief. Robert McClenon (talk) 21:07, 5 September 2021 (UTC)


 * Regardless of how ivermectin is produced – which IMO is irrelevant to the origin of (incorrect) stories about the presumed efficacy of ivermectin in treating COVID-19 – there is a rational basis for its consideration. In a controlled in vitro study, a 5000-fold reduction in viral RNA after exposure to ivermectin compared with control was found in cells infected with the SARS-CoV-2 virus. Unfortunately, this did not translate to good results in clinical trials. --Lambiam 21:46, 5 September 2021 (UTC)
 * Yes, according to the 1983 source and 2017 "Ivermectin – Old Drug, New Tricks?": it's a purified product treated by reaction with hydrogen (hydrogenation). I can't find an explicit statement of why the bacteria make it, but it seems likely. Blythwood (talk) 00:25, 6 September 2021 (UTC)
 * Infinite-fold virus reduction is easy, just eat ivermectin until dead and if that fails dissolve body in acid until nothing left. Sagittarian Milky Way (talk) 00:47, 6 September 2021 (UTC)
 * That approach works in a sense, but it's close kin to throwing the baby out with the bathwater. ←Baseball Bugs What's up, Doc? carrots→ 03:41, 6 September 2021 (UTC)
 * [//www.science.org/content/blog-post/s-up-ivermectin] [//www.chm.bris.ac.uk/motm/ivermectin/ivermectinh.htm] also seem to confirm. Nil Einne (talk) 09:21, 6 September 2021 (UTC)
 * To answer your question,, Ivermectin describes the production process. The bacterium is Streptomyces avermitilis and it produces avermectins, as described in this book chapter. As with other pharmaceutical products, the strain of S. avermitilis used in production now will have been considerably optimised for yield. The avermectins were mainly developed as commercial insecticides. Ivermectin is a synthetic derivative in which one of the double bonds is reduced by hydrogenation and this is the compound mixture marketed as an antiparasitic agent for human use. Your suggestion that the bacterium gains a competitive advantage by poisoning other soil organisms is plausible but I don't think that this has been established. Mike Turnbull (talk) 10:44, 6 September 2021 (UTC)