Wikipedia:Reference desk/Archives/Science/2021 March 12

= March 12 =

Titanium swords and knives
I was curious why most knives and swords seem to be made from traditional forms of metal and not the much more durable titanium.--85.4.148.47 (talk) 01:59, 12 March 2021 (UTC)
 * They do exist, but most titanium alloys are softer than hardened steel, so it's difficult to get it to hold an edge.
 * A Ti sword would be a lot lighter than a steel sword of the same size, which isn't necessarily a good thing, especially you want your sword to be the same size and shape of a particular style of traditional steel sword. ApLundell (talk) 06:09, 12 March 2021 (UTC)
 * Although it must be noted that replica swords in general often differ from original ones in weight and balance, anyway (see e.g. here). Cheers ⌘  hugarheimur 09:14, 12 March 2021 (UTC)
 * Titanium wasn't discovered until late in the 18th century. Was there still very much swordfighting going on by then? ←Baseball Bugs What's up, Doc? carrots→ 07:07, 12 March 2021 (UTC)
 * Military officers used/carried swords until about WW1, when it was realized that singling them out to enemy snipers might not be such a good idea after all (and btw, "discovery" doesn’t necessarily equate to practical usability). ⌘  hugarheimur 09:15, 12 March 2021 (UTC)
 * Bernard Montgomery famously led an infantry charge with his sword in October 1914, but when confronted by a large German, realised that he had never been trained how to use it and resorted to kicking him instead. There were a surprising number of horsed cavalry charges with swords in the Second World War, the last seems to have been at the Battle of Schoenfeld in 1945. Alansplodge (talk) 15:32, 12 March 2021 (UTC)
 * It's not surprising; the lack of experience defending against the tactic probably made quite successful. A herd of horses bearing down on a bunch of rifle carrying infantrymen was probably as unnerving to the defenders in 1945 as it was in 1745.  The rifle is an important weapon, but its effectiveness in combat as a fire arm was not that much of an advantage; arguably the bayonet and the shovel were more important in pitched combat than a rifle.  Erich Maria Remarque sung the praises of the shovel as an effective weapon.  Hand-to-hand weapons like knives, bayonets, and shovels don't jam like guns and require little skill to aim; a good heavy shovel can break bones and shatter skulls, and Remarque even notes that a well sharpened shovel expertly swung could cleave a man's chest.  Good tactics, execution, and sheer balls are still an advantage over technology.  -- Jayron 32 19:28, 12 March 2021 (UTC)
 * Probably not used much in combat, but don't forget that classic woman's weapon: a heavy frying pan. --142.112.149.107 (talk) 21:16, 12 March 2021 (UTC)
 * Indeed. Titanium metal was not produced in both sufficient quantities and a form suitable for making macroscopic components until the Second World War era: see Hunter process and Kroll process. My (maternal) grandfather was a machinist, a reserved occupation during the War, and worked in a British laboratory on a project to achieve this. Some time in the 1970s he showed me a small billet of the metal with a hacksaw cut in it, and told me it was the first successful sample produced, and that he himself had made the cut as a demonstration of its machinability. {The poster formerly known as 87.81.230.195} 2.125.75.168 (talk) 13:36, 12 March 2021 (UTC)
 * The Pros and Cons of Titanium Knives mentions the US Navy SEALS titanium knife. Alansplodge (talk) 15:47, 12 March 2021 (UTC)

Properties of a macroscopic amount of virus
The mathematics YouTube channel Numberphile just published a video entitled "All the World's Coronavirus Fits in a Coke Can" in which mathematician Kit Yates makes a Fermi estimate that all the SARS-CoV-2 coronavirus particles in the world would fit in a can of Coca-Cola (thereby missing the opportunity to make the pun that they would fit in a can of Corona beer).

What would the physical and chemical properties of such a macroscopic amount of coronavirus -- or even viruses in general other than coronavirus -- particles be? Would the mass as a whole seem solid or liquid-like? Would it be sticky? Would the viral particles attract or repel each other? What would it look like? Would it be transparent or opaque? What color, texture, smell, or other physical and chemical properties would it have?

—SeekingAnswers (reply) 10:27, 12 March 2021 (UTC)
 * Optically, it would almost certainly be opaque. Viruses are close in size to the wavelength of light (our article says that 50–200 nanometres in diameter per each SARS-CoV-2 virion), so that light scattering (specifically, Mie scattering) becomes relevant. Considering that those virions are 90+% water, the immediate analogy is a cloud, which can be opaque even though particles are much more dispersed than the case we suppose here.
 * Surface proteins and whatnot are probably important factors in whether virions attract, repel, stick together etc., maybe someone else can tackle that aspect. I would think virions are large enough (compared to the scale of molecular interactions) that there is no long-distance attraction or repulsion between them, but still small enough that Brownian motion is a concern and intuitions about standard granular materials (e.g. sand) go out of the window. Tigraan Click here to contact me 11:06, 12 March 2021 (UTC)
 * There is a well-know radio program in the UK called "More or Less" which discussed this topic on 13 February this year. You can listen to it . The two mathematicians they consulted concluded the answer was "about 160 ml" and "about 8ml" and explained the basis of their estimates. They didn't discuss the physical or chemical properties. Mike Turnbull (talk) 13:02, 12 March 2021 (UTC)


 * Viruses are basically protein, lipid and water. If we look for an analogue in our own experience, eggs come to mind.  I expect something like a beaten egg would provide a similar consistency, though that's just a guess. -- Jayron 32 13:15, 12 March 2021 (UTC)


 * XKCD once wrote an article that briefly speculates on collecting viruses in one place, he suggests "[It's hard to predict exactly what it would look like] but it would probably resemble something in between pus and meat slurry. Regardless of its exact appearance, it would almost certainly be disgusting."
 * ApLundell (talk) 17:48, 12 March 2021 (UTC)


 * The classic science demonstration, extraction of DNA from strawberries, comes to mind: here is an example lesson-plan / Teacher Guide for Strawberry DNA Extraction. It is not difficult to find online videos demonstrating the entire process and its result.  The technical term for the macroscopic product that is captured in the inoculating loop is a "deoxyribonucleic acid (DNA) precipitate", but you could be well-understood by most scientists if you called it "goop."  Here is a video demonstration from the NC State Cooperative Extension, one of many thousand similar educational demo-videos that can be easily located on the web.
 * "To first order," this "goop" is pure and unadulterated nucleic acid. The physical chemist might quibble about how impure that "goop" really is - it almost surely also contains "gunk" - (other, undesired biological molecules) - because this kind of elementary extraction method isn't highly refined - after all, it's a simple classroom version of a real lab process.  And it's not dry - even "pure goop" also contains water, or ethanol, or what-ever-other-solvent your particular experimental demonstration uses.  It might be reasonable to say that the macroscopic properties are largely dominated by the nucleic acid molecules - but at the same time, ... wet chemistry has a lot of caveats.  After all, in chemistry, we often find that adding a tiny tiny tiny fraction of impurity has a very significant effect on macroscopic properties.  We might equally say that the macroscopic properties of the nucleic acid strongly depend on any solvent in which the molecules are in: all the "wet" stuff might be ethanol, or water, and so on - and if we desiccate the final product, it might behave very differently.  Consider, if you will, the "macroscopic properties" of ordinary table salt (NaCl) in various mole fraction combinations with ordinary water (H2O): consider ratios of 10,000:1, 10:1, 1:1, 1:10, 1:10,000 ... exactly which macroscopic properties are those of the salt, and which are those of the salt-as-a-solute-in-water?  (Electrical conductivity springs to mind!)  And salt is a very simple, well-understood chemical - it is much harder to completely and correctly describe all the physical properties of a complicated organic molecule!
 * The original post even asked about color - well, golly, color is almost the textbook example of how a 1-part-per-billion impurity can change the optical properties of a macroscopic sample! Indeed, dye and pigment are the jargons we use to specifically differentiate how color chemistry depends on solvent!
 * One imagines that the "goop" that precipitates from macroscopic quantities of virus would be structurally similar. There might be many follow-up questions for which I do not have all the answers: can similar chemistry (lysis) be applied to virus, or is this procedure specifically applicable to the plant cells from which strawberries are built?  Could a different chemistry experiment be designed that would extract macroscopic quantities of the virus nucleic acid?  When we speak about macroscopic quantities of "virus particle," do we accept a lysis precipitate, or is there a strict requirement that we want to keep virus superstructures (like the capsid of a corona-type virus) intact?  I imagine these questions are not difficult to an expert who has formal training in microbiology - nucleic acid extraction is pretty standard stuff in molecular biology labs.
 * Nimur (talk) 19:14, 12 March 2021 (UTC)

Regular shaped viruses can be packed neatly into a crystalline lattice. So here is a picture of one. Graeme Bartlett (talk) 20:00, 12 March 2021 (UTC)