Wikipedia:Reference desk/Archives/Science/2019 May 1

= May 1 =

query

 * What causes a stuffy nose and sore throat? -- Thegooduser  Life Begins With a Smile :)  🍁 01:34, 1 May 2019 (UTC)
 * Have you read our articles on stuffy nose and sore throat? As they explain, these symptoms are not very specific and have numerous possible causes. Note that the Ref Desk doesn't give advice on medical diagnosis or treatment; if you have these symptoms and desire help, you should consult a medical professional. --47.146.63.87 (talk) 02:35, 1 May 2019 (UTC)

Which finger is wider than others?
Out of the 5 fingers that people have in one hand, it's clear that the widest one is the thumb while the narrowest one is the pinky finger. My question is about the rest (index, middle and ring fingers), which one of them wider than the other? I tried to find some scientific reference about it but I didn't find (maybe due to language barrier or searching incorrectly or combination of both of them), maybe you know? 93.126.116.89 (talk) 02:18, 1 May 2019 (UTC)
 * What, you don't know which of your own fingers is your widest? ←Baseball Bugs What's up, Doc? carrots→ 02:51, 1 May 2019 (UTC)


 * One of the foundational works on biometrics was The "Average Man"? (USAF, 1952). Beware of using average human-body-size dimensions, because they are misleading - there are many pitfalls associated with statistics pertaining to human feature-sizes.
 * That paper studies the issues, and then cites some more publications that aggregated data and reported human body-part sizes - which is the field known as anthropometry.
 * Whenever I encounter people who are fixated on biometrics, especially as it pertains to modern computer software systems, I also like to remind them that modern biometrics is the direct academic grandchild of the now-discredited field of phrenology. Something about collating vast databases of finger statistics always seemed a little bit ... obsolete and regressive.
 * Nimur (talk) 04:27, 1 May 2019 (UTC)
 * One of my favorite biometric statistics is that the average number of legs is less than two. — Preceding unsigned comment added by 2a01:e34:ef5e:4640:6931:b103:3c9d:4641 (talk) 06:40, 1 May 2019 (UTC)
 * Likewise, my high school maths teacher was keen on pointing out that 100% of people who breath oxygen die. Iapetus (talk) 08:12, 1 May 2019 (UTC)
 * The average adult has one breast and one testicle. DMacks (talk) 16:31, 4 May 2019 (UTC)
 * Meaning the arithmetic mean. This illustrates how the word "average" is vague and it's clearer to just explicitly state the measure you're referring to. The mode of the number of human legs is, of course, two. --47.146.63.87 (talk) 21:13, 1 May 2019 (UTC)

The Ice Wall in Game of Thrones
Background: The TV showw Game of Thrones has a 700 foot tall ice wall Various social media sources contain speculation that such a wall is impossible (giants, dragons, ice zombies and a fireproof queen are OK, but an ice wall? That's going too far!) and speculation that it isn't actually ice, but rather pycrete.

This led to mutiple new editors adding unsourced claims to the pycrete article. When it was semi-protected, they started adding unsourced material to Project Habakkuk and Geoffrey Pyke.

Which brings me to my question.

Pykrete contains the following claim:

The durability of pykrete is still debated. Perutz has estimated a crushing strength value of around 1100 psi.

A September 1943 proposal for making smaller pykrete vessels included the following table of characteristics:

But this ref says "Concrete with compressive strengths greater than 10 ksi (69 MPa) is now available commercially as a result of improvements in concrete admixtures and the quality control process in plants."

So I thought I would update the table with figures for modern concrete, change "crushing strength" to "comprehensive strength", and add prestressed concrete (or perhaps reinforced concrete) to the table (regular concrete has a very poor tensile strength).

I am also curious about the strength of ice against slow deformation (as in glaciers flowing) vs sudden failure. And does pycrete actually change the slow flowing of ice? The G.O.T. fans would be happy if we found an answer to that one. Perhaps the existing Perutz (1948) ref covers this? It does have "glaciers" in the title...

I am having a heck of a time finding sources that directly address these questions. Does anyone know of a source that lists the strength at least the ice and normal/prestressed concrete? --Guy Macon (talk) 05:57, 1 May 2019 (UTC)


 * Have you consulted the ASME handbook, the ASCE handbook, or the CRC handbook of chemistry and physics?
 * CRC Civil Engineering Handbook
 * CRC Handbook of Chemistry and Physics
 * ...several dozen ASME handbooks
 * ...I find that using these handbooks gets me my data faster than a general-purpose internet-search. If you don't own any of them, they're usually available in the technical library at the local engineering college or university.
 * Nimur (talk) 16:06, 1 May 2019 (UTC)
 * Even a small public library branch might have the CRC Handbook of Chemistry and Physics too. Mine did. Sagittarian Milky Way (talk) 02:02, 2 May 2019 (UTC)


 * I think I read somewhere that something like this was discussed:


 * Show creators: And this is how the Wall will look!
 * Martin: But that's far too big, people can't build that!
 * Show creators: It's according to what you wrote in the book.
 * Martin: Really? Didn't think that through, then. Gråbergs Gråa Sång (talk) 08:20, 2 May 2019 (UTC)

Li-ion battery aging: electric cars vs smartphones
Smartphones with old batteries sometimes suddenly lose power when the user interface indicates they are, say, 30% charged. How do electric cars (with no backup gas tank) prevent this problem as their lithium-ion batteries age? I know an engine tends not to have an all-or-nothing response of functionality to voltage the way a smartphone CPU does, but would the reduction in horsepower necessarily be gradual enough for drivers to handle safely? Neon Merlin  16:29, 1 May 2019 (UTC)
 * Just as in cellphones, lithium ion batteries in electric cars lose some of their storage capacity per year even if they are not used. However in the electric car a much larger battery pack of many cells in series is arranged to supply some hundreds of volts, and the many cells are unlikely to age equally. Usually there is monitoring of groups of cells and failure of just one cell produces a warning but the car remains driveable. Experience of traction battery reliability in cars has been good with Toyota concluding that "EVs can therefore match or exceed the lifecycle miles of comparable internal combustion engine vehicles." Hybrid electric vehicles such as the Prius offer the greatest surety against being stranded by a traction battery failure since the car (with its gas tank) can proceed at reduced power using its gasoline engine only. DroneB (talk) 17:44, 1 May 2019 (UTC)
 * Battery management on electric vehicles is also much better. As stated above, each cell is individually monitored and the charging of each is adjusted to ensure that all cells are equally charged.  Charge rates are reduced when the cells are close to full charge to avoid damage.  Owners are warned to charge the car if the battery is close to fully drained.  The management software allows for reserves which are never fully charged or discharged.  On my i3 the battery pack has temperature control and is heated if too cold and cooled if too hot.  My previous i3 travelled over 40,000 miles over 4 years and I noticed no degradation at all.--Phil Holmes (talk) 09:15, 2 May 2019 (UTC)

which one is stronger in taste- sugar or salt?
I have an hypothetical question about sugar and salt: If we take a table sugar (sucrose) and a table salt and we put the same molecular mass in a water. Will it be salty or sweet or natural or both salty and sweet simultaneously? 93.126.116.89 (talk) 17:58, 1 May 2019 (UTC)
 * Mass-for-mass, salt water would be more concentrated than sugar water. That's because sodium chloride has a molar mass of 58 and sucrose has a molar mass of 342.  That means that you're getting almost 6 times as many formula units of salt; and thus six times as many opportunities to activate your taste receptors.  I have no idea if the ability of salt vs. sweet taste receptors has been quantified, but on a purely chemical level, putting the same mass of each in water will result in much higher salt concentration.  -- Jayron 32 23:15, 1 May 2019 (UTC)
 * Salt isn't a compound, so it's useless to look at empirical formula. In reality, it isn't NaCl, but Na(1 million)Cl(1 million). 170.76.231.162 (talk) 01:16, 2 May 2019 (UTC).
 * Sodium chloride commonly known as salt is an ionic compound with the chemical formula NaCl. Jayron32's Molar mass calculation is correct, not "useless". DroneB (talk) 01:38, 2 May 2019 (UTC)
 * Indeed, 1 gram of sodium chloride would contain about 6x the sodium ions as 1 gram of sucrose would contain sucrose molecules. The fact that it is an ionic compound is not useless.  When you put the salt on the scale and weigh it, you weigh equimolar amounts of sodium ions and chloride ions, which is why the formula is NaCl, and why the molar mass is 58ish.  The fact that the salt dissociates in water doesn't change the fact that there are equal numbers of atoms of each sodium and chlorine.  -- Jayron 32 12:38, 2 May 2019 (UTC)
 * In addition to perception effects (i.e. salt vs. sugar taste receptors), one should also note that the solubility of salt in water (in g/L) is lower than that of sugar (source comparing the two). If you put enough of both to saturate salt but not sugar, you would comparatively get more sugar mass in solution.
 * Interestingly, the graph of solubilities there has sucrose in the vicinity of 6–7 times the solubility on a mass basis as NaCl at room temperature, so the solubilities are actually pretty close on a molar basis (or NaCl is almost twice as soluble on a particle basis). And also interesting is that sucrose (but not NaCl) has a strong temperature dependence. DMacks (talk) 19:24, 2 May 2019 (UTC)
 * Why sugar is more soluble than salt would be a good question (when searcing a source, I assumed salt would be more soluble since water is a highly polar solvent, but my chemistry is apparently lacking). Tigraan Click here to contact me 09:38, 2 May 2019 (UTC)
 * Sugar contains a very large number of hydroxyl groups, each of which adds to the solubility. Sodium and chloride ions, while being low charge (each has a charge of 1), also have a fairly small ionic radius, which means that each will only be able to surround itself with a relatively small number of water molecules before they start being so close to each other that they start bonding to each other and settling out of solution.  Sodium chloride is quite soluble for an ionic compound, but there are many polar covalent compounds which are essentially infinitely soluble in water (often those that feature hydrogen bonding); we call that fully miscible.  At near boiling, you can create just about any arbitrarily concentrated sugar solution.  As the solution cools, rather than precipitating sugar, it will slowly become more viscous until reaching an amorphous solid-type phase, but you don't get a sugar precipitate as with a salt.  This well known to candy makers, who take advantage of this to create a wide variety of candy types from different sugar solution concentrations.  Hydroxyl-containing liquids, like ethanol, display this miscibility even better.  -- Jayron 32 12:47, 2 May 2019 (UTC)
 * Just an addendum; you can get sugar to precipitate under some conditions, for example when making rock candy; in those cases seed crystals of sugar can be used to grow sugar crystals in a super-saturated solution. But depending on how you get to that "super-saturated" state can change how the sugar solution behaves.  Solution behavior is complex as the molecules get more complex.  With most ionic compounds, especially those of simple monatomic ions that do not themselves form coordination complexes with water, and where there is no hydrogen bonding (i.e. when you are basically solvating hard little charged spheres) they behave rather simply.  However, when you get big, squishy, messy molecules like sucrose, the behavior becomes far more complex.  --16:32, 2 May 2019 (UTC)
 * In addition to the above, it's also worth noting that it may be impossible or impractical to compare sweet and salt taste as they may actually be linked, at least to some extent. Our sweet taste receptors have glucose transporters, which are actually co-transporters with sodium ions. This means that, in order to transport glucose to the taste receptors, they need sodium ions. To some extent, I'd imagine this is already present in our saliva, but this is one of the reasons why it's good to add a little salt to dessert recipes. For example, when I make chocolate fudge, I add a little salt, not enough to make it taste salty, but it definitely kicks up the sweet factor. --OuroborosCobra (talk) 19:23, 4 May 2019 (UTC)