Wikipedia:Reference desk/Archives/Science/2019 February 26

= February 26 =

Is there a scientific basis for the claim that the 3rd day after an injury is the most dangerous or painful?
Is there a scientific basis for the claim that the 3rd day after an injury is the most dangerous or painful? In the bible is written "On the third day, when they were sore, two of the sons of Jacob, vSimeon and Levi, wDinah’s brothers, took their swords and came against the city while it felt secure and killed all the males." Some classical Jewish interpreter of the bible explained, based on this verse, that the third day is considered the most painful or dangerous for an injury. I'd like to know if this claim as a basis in a science or it is wrong.93.126.116.89 (talk) 04:49, 26 February 2019 (UTC)


 * From the United States' National Institutes of Health, I found the following review article, which is an introduction to the subject written by several pharmacologists:
 * Clinical aspects of acute post-operative pain management and its assessment (2010).
 * That article cites many additional sources, and the NIH website links to many similar articles in other professional publications.
 * Nimur (talk) 05:32, 26 February 2019 (UTC)
 * If I understand, it says no scientific basis for this claim. Thank you. 93.126.116.89 (talk) 05:42, 26 February 2019 (UTC)
 * Presumably the "they" who were sore were Shechem and the other males of the city, not Simeon and Levi despite the ambiguosity in English, because 3 days earlier they had been circumcised, a likely more serious and slower-healing injury for an adult male than for a 8-day-old infant. It can reasonably be supposed that the city men were still sore, but there is nothing in the English translation to impy that they were more sore than on the previous day. Is this present in the original Hebrew text? {The poster formerly known as 87.81.230.195} 2.122.1.40 (talk) 13:48, 26 February 2019 (UTC)
 * I will note that the source text does not say that they were sorest on the third day, so that interpretation is a novel one and not based on anything in the source writing. It merely says they were sore on the third day, without a comparison to any other day.  -- Jayron 32 19:19, 26 February 2019 (UTC)
 * NIV puts it "Three days later, while all of them were still in pain, two of Jacob’s sons..." which is consistent with the above comments. Wnt (talk) 02:09, 3 March 2019 (UTC)


 * There is no general timeframe for healing. A young, trained Athlete can heal off a small Abrasion (medical) in under one day (that often surprised me in my youth) while the same injury may take 1-3 Weeks now to repair, since i am old. Similar with sicknesses. Dependent if the person has a strong, trained Immune system or not, often independent from age. Some are only 2-3 days ill from an Influenza which others unfortunately wont survive. --Kharon (talk) 20:35, 26 February 2019 (UTC)

guide us about the black holes with standard references
there are so many misunderstanding about black holes, according to Chandrasekhar limit  star core with 1.4 times  massive than sun can be black hole , the process ending supernova formation , only create neutron star , up to now Contrary to opinion theoretical astrophysicist's ,man has never been able to observe supernova core containing black hole. I think it will be changed in theoretical field too ,based on observation.--Akbarmohammadzade (talk) 06:48, 26 February 2019 (UTC)
 * Who are you talking about? ←Baseball Bugs What's up, Doc? carrots→ 07:17, 26 February 2019 (UTC)

me an astrophysics researcher ,real and fact information needed. thank you. --Akbarmohammadzade (talk) 08:33, 26 February 2019 (UTC)
 * Who is Chandrasekhar? ←Baseball Bugs What's up, Doc? carrots→ 08:36, 26 February 2019 (UTC)Chandrasekhar
 * Come on, Bugs. Use of the name "Chandrasekhar" with the term "black hole" in the same sentence makes it obvious which person is being referred to, if you know even the most elementary background about black holes. (And if you don't, why are you answering this question?) We even have an article about the term Chandrasekhar limit mentioned in the OP which you could have looked up even though the OP did not link it. CodeTalker (talk) 14:10, 26 February 2019 (UTC)

until now, the specimen has shown that the star has not been seen at the end of its life as a black hole. The whole story of a star becoming black hole at the end of life is almost eliminated--Akbarmohammadzade (talk) 08:44, 26 February 2019 (UTC)
 * So you're talking about Subrahmanyan Chandrasekhar? ←Baseball Bugs What's up, Doc? carrots→ 08:45, 26 February 2019 (UTC)
 * Have you read our article about black holes? There are plenty of references there. Do you have a question about that article?--Shantavira|feed me 10:16, 26 February 2019 (UTC)


 * As I understand, you are claiming that because nobody ever happened to be watching a star collapse into a black hole, it must not have ever happened and all of science is a sham. The reason it hasn't been seen is because space is huge. It is really huge. You might think it is a long walk to the corner store, but that is just peanuts compared to space. So, how do you watch all of it at once? You can't. Scientists watch what they can when they can. Luckily, on Jan 11, 2019, scientists were lucky enough to see the flash of a super nova in a distant dwarf galaxy. Now, we are waiting for the afterglow to finish. Then, we will see if it collapsed into a neutron star or a black hole. We are just waiting. Why not grab some popcorn and wait with us. 209.149.113.5 (talk) 14:16, 26 February 2019 (UTC)


 * [Edit Conflict] The OP is mistaken about the Chandrasekhar limit. This, about 1.4 times the Sun's mass (1.4 M☉), is the mass limit above which the white dwarf remnant of a Nova or Supernova will collapse, but this will usually be to a Neutron star (which may also be a Pulsar). To collapse further to a Black hole requires the white dwarf remnant to exceed the Tolman–Oppenheimer–Volkoff limit, around 3–4 M☉ (unless quark pressure comes into play), which will be rare because a supernova doesn't usually leave a white dwarf that big.
 * We have not directly observed a supernova result in a black hole because supernovae are rare on a human timescale. The last one observed in our Galaxy was in 1604 (the one in 1899 ±9 years wasn't visible at the time, its remnant was only detected in 1984), and stellar-mass black holes are hard to detect, particularly if all nearby material has just been blown away so that they experience little or no infall. Supernovae in other galaxies are certainly too distant for us to currently be able to detect a resultant stellar-mass black hole.
 * Long story short: we haven't identified a black hole produced by a supernova yet because nearby supernovae are rare, they will only sometimes produce a black hole, and that black hole would be very difficult to detect. Our expectable failure to date doesn't disprove anything about the theory, any more than our failure to directly detect gravitational waves before 2016 disproved their existence. {The poster formerly known as 87.81.230.195} 2.122.1.40 (talk) 14:33, 26 February 2019 (UTC)

many thanks — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 03:51, 1 March 2019 (UTC)


 * This isn't exactly what you asked for, but a neutron star merger has recently been observed by gravitational wave observation, producing a jet likely to have originated in a black hole. Wnt (talk) 02:13, 3 March 2019 (UTC)

Calculations of observable universe
Is there an article here (or external reference) explaining the math behind current observable universe radius? I tried to use Hubble's law as a linear approximation and found that value should be 37 bly, didn't get similar result of 46.1 bly. I may be missing other information on calculation. Thank you, Almuhammedi (talk) 17:30, 26 February 2019 (UTC)
 * Does Observable universe help? It doesn't mention Hubble's law, but discusses other models and calculations to determine the size of the universe.  -- Jayron 32 17:44, 26 February 2019 (UTC)
 * Unfortunately, it still doesn't explain how the 46.5 was achieved mathematically. Almuhammedi (talk) 04:05, 27 February 2019 (UTC)
 * What you're looking for is in this book reference:, which shows how to calculate the distance to a light source based on redshift, scale factor and Hubble's constant. The book actually shows the derivation of this relationship in a variety of general relativistic models, and this formula belongs to the flat version of the FLRW metric. This relationship depends on assumptions about the nature and history of the universe, but there is considerable agreement that the universe looks like flat FLRW back to the time of last scattering. Someguy1221 (talk) 04:42, 27 February 2019 (UTC)

Thanks. I also searched other web, found an online explained proof here on Quora. What surprised me was another research doing simpler calculations, using a 3-Sphere Model, which I am not sure if can be considered an accepted model.Almuhammedi (talk) 05:23, 3 March 2019 (UTC)
 * Yes, that proof uses the Friedman equations, which are related to the FLRW metric (indeed, the "F" in there is for "Friedman"). That 3-sphere model was "published" by an amateur who as far as I can tell holds no academic position and has never been published in a proper journal. I would not consider anything he writes to be accepted. Someguy1221 (talk) 10:30, 3 March 2019 (UTC)