Wikipedia:Reference desk/Archives/Science/2021 May 4

= May 4 =

Red blood cell production following blood loss
Hi. Multiple sources say that the about 2 million new red blood cells are created every second in the human body under normal circumstances. But what is the corresponding figure when the body needs to replenish its red blood cells following significant blood loss? Thanks.
 * I seem to recall that the body does not increase the rate of production of rbcs, but rather decreases the rate of destruction of rbcs in the spleen until the low blood count is improved. Abductive  (reasoning) 01:02, 4 May 2021 (UTC)
 * The body most certainly increases the production of red cells following significant blood loss. In cases of chronic blood loss, yellow (inactive) bone marrow may be converted to red (active) bone marrow, to increase the volume of blood-producing tissue. In extreme cases, tissues that normally do not produce red blood cells in the adult (liver, spleen), may start doing so (extramedullary hematopoiesis). The count of recently-produced red cells (reticulocytes) in the blood increases. Red blood cell production, as measured by bone marrow iron consumption, can increase up to 10-fold (reference). --NorwegianBluetalk 07:21, 8 May 2021 (UTC)

What does "acceleration" purpose in mechanics?
We say acceleration due to gravity is 9.8 m/sec2. But I say speed of freely falling object on Earth is equal to 9.8 m/sec without using acceleration. So What does "acceleration" purpose in mechanics? Rizosome (talk) 07:05, 4 May 2021 (UTC)
 * 9.8 m/sec2 can be said as "nine point eight meters per second, per second", meaning that the velocity increases by 9.8 m/s every second (ignoring air resistance). That's the difference between velocity ("speed") and acceleration. Speed is a constant, whereas velocity isn't. 2603:6081:1C00:1187:1110:9627:D5D8:97F4 (talk) 07:14, 4 May 2021 (UTC)^
 * You must have meant to write "Acceleration is constant", not "speed is a constant", I think. Jmchutchinson (talk) 19:25, 4 May 2021 (UTC)

What about speed of freely falling body? Is it undetermined? Rizosome (talk) 07:22, 4 May 2021 (UTC)


 * The speed will change (accelerate) until terminal velocity is reached.--Shantavira|feed me 07:46, 4 May 2021 (UTC)

So for a free falling object have two values: speed and velocity? Rizosome (talk) 07:51, 4 May 2021 (UTC)
 * Speed and velocity are essentially the same thing. Acceleration is change in speed over time. ←Baseball Bugs What's up, Doc? carrots→ 11:10, 4 May 2021 (UTC)
 * If there was no air resistance then a falling object would accelerate with 9.8 m/sec2 until hitting the ground. That means that if it starts at rest then after 1 second it would have velocity 9.8 m/sec. After two seconds it would be 19.6 m/sec. After 3 seconds it would be 29.4 m/sec, and so on. (Some small factors are ignored here). PrimeHunter (talk) 11:21, 4 May 2021 (UTC)
 * As noted in Gravitation of the Moon, its number is 1.625 m/s2. Since there is almost no atmosphere on the Moon, any object falling toward the Moon will continue to accelerate at that rate until it hits the surface. ←Baseball Bugs What's up, Doc? carrots→ 11:30, 4 May 2021 (UTC)
 * I don't really understand this.  A quadratic equation (involving x squared) presents on a graph as a parabola.   If you plot the figures presented by PrimeHunter (velocity against time) they present as a straight line. 95.148.229.85 (talk) 13:11, 4 May 2021 (UTC)
 * The quadratic equation graph is of displacement(i.e. distance covered) against time and Prime hunter told about velocity against time which plots as straight line -- Parnaval (talk) 13:24, 4 May 2021 (UTC)
 * So is the velocity increasing at a uniform rate or not?  If it's plotted against seconds (1, 2, 3 etc) then it's a straight line, but if it's plotted against seconds squared it can't be - after 1 second the velocity is x, after 2 seconds 4x, after 3 seconds 9x, and so on. 95.148.229.85 (talk) 13:52, 4 May 2021 (UTC)
 * The velocity is increasing at a constant rate; if you plot the speed vs. time on a graph (assuming acceleration is in the same direction as the motion) then the line will be straight and the slope of the line is the acceleration. If the line were not straight, that would mean that the acceleration were changing, and then we go another level deeper, there's a function called Jerk, which is the change in acceleration over time, and ITS units would be distance per unit time cubed (i.e. m/s/s/s or m/s3).  There are even functions if jerk varies with time, see Fourth, fifth, and sixth derivatives of position, and after that it's turtles all the way down.  -- Jayron 32 13:58, 4 May 2021 (UTC)
 * If it had been presented as 9.8 metres per second per second I think that would have been clearer. 95.148.229.85 (talk) 14:02, 4 May 2021 (UTC)
 * Maybe. m/s2 = m/(s⋅s) = (m/s)/s. Physicists prefer to only write a unit once, and often to use negative exponents instead of division. m/s2 = m⋅s−2. It can get much worse. From farad: In SI base units 1F = 1s4⋅A2⋅m−2⋅kg−1. PrimeHunter (talk) 14:27, 4 May 2021 (UTC)
 * From a mathematical point of view, it makes no difference. The notation is unconnected to the operation, and you can write it as m/(s.s) or m/s2 or m/s/s or (m/s)/s or m.s-2 or whatever works for you.  It's all the same.  It's the distance, divided by time, divided by time again.  Or square the time and take the distance and divide it by the result of that.  As long as the dimensional analysis works out, it's acceleration if the units reduce to m/s2.  Now, the meaning of that acceleration changes depending on how you calculate it; it can be instantaneous acceleration or average acceleration (of which there are several ways to mean "average") or initial acceleration, or whatever, and the meaning of the calculation will change depending on the method used to calculate it (including being relatively useless for modeling real behavior...) but it's still acceleration if it's got that set of units.  -- Jayron 32 11:56, 5 May 2021 (UTC)
 * Primehunter actually reminded me of a side discussion I sometimes hold in my chemistry class when we discuss the universal gas constant and why it shows up BOTH in the ideal gas law, AND in several different equations where energy pops out. The units of the standard form of the gas constant, R, are something like (liter.kPa)/mole.K) when you use it in the Ideal Gas Law, but are something like J/mole.K when you use it in thermodynamics applications, and the reason for that is that volume times pressure is energy.  The fact that this doesn't seem to make physical sense (volume and pressure are bulk properties of a gas, whereas energy tells you something about how an object will move) is not really that important here; volume times pressure is energy because the units are the same (energy is J, which is a N.m, and since a Newton is a kg.m/s2 that means a joule is a kg.m2/s2.  Pressure is measured in pascals, which is N/m2.  That's means a pascal is a kg/m.s2 and volume is m3.  So pressure times volume has units of kg.m2/s2 the same as energy, QED.  -- Jayron 32 12:08, 5 May 2021 (UTC)


 * I agree with Jayron32! Bernoulli's principle is sometimes written as follows:
 * $${\rho} \frac{v^2}{2} + \rho gz + p = \text{constant}$$
 * where the first term is the kinetic energy of a unit volume of fluid; the second term is the potential energy of a unit volume; and the third term is simply static pressure. It shows that static pressure is a measure of some of the energy in a unit volume of fluid. Dolphin ( t ) 12:32, 5 May 2021 (UTC)
 * One of the things that makes energy so hard to grasp as a concept is that energy is not itself observable, it is an abstract property of a system, and it isn't "stored" or "created" and doesn't really even have an existence, though we tend to visualize it as a fluid that can move from place to place or some substance we can store like phlogiston or caloric or Luminiferous aether or something like that, it's just a number we assign to a system that quantifies how much that system has the potential to cause a change to occur. Energy as a concept has certain mathematical properties and symmetries that make it a conserved quantity, and that make it a transferable quantity, but it's not a tangible stuff or thing or anything.  It's just a number we assign to a system of objects or particles that says "this system has the ability to alter motion in by a certain amount".  That number has units of mass times velocity squared, but merely because it has units doesn't mean it is tangible.  Any mathematical operation we can do with other measurements that spits out "mass times velocity squared" is, by definition, a calculation of energy content.  That energy content can, hypothetically, be transformed into other energy content, though whether that is practical to do or even physically possible is a different story, but it still is all just energy, whether it is the Bernoulli term you brought up, or the pressure times volume of a gas, or a massive object moving at some constant speed, or a photon of light, it's all energy.  -- Jayron 32 12:43, 5 May 2021 (UTC)

Etymology of "aeroplane"
The word "aeroplane" was apparently coined by French sculptor and inventor Joseph Pline in 1855. What was that paper? Is it available online? Andy Mabbett ( Pigsonthewing ); Talk to Andy; Andy's edits 09:47, 4 May 2021 (UTC)
 * The term preceded the modern usage. ←Baseball Bugs What's up, Doc? carrots→ 11:14, 4 May 2021 (UTC)
 * The self-published page you link to gives "French aéroplane (1855)... Ancient Greek had a word aeroplanos, but it meant 'wandering in the air'". Andy Mabbett ( Pigsonthewing ); Talk to Andy; Andy's edits 11:26, 4 May 2021 (UTC)
 * Your uncited claim about the origin of "aeroplane" is likewise self-published. ←Baseball Bugs What's up, Doc? carrots→ 11:46, 4 May 2021 (UTC)
 * It was in a patent apparently:
 * M. Joseph Pline, breveté en juin 1855, pour un système mixte l'Aéroplane , dont je me réserve de dire quelques mots , avait fait du plan – le nom de son appareil l'indique , - la base d'un système absolument différent de tous ceux qui ont l ' aérostat pour point de départ... Il proposait de construire un appareil dirigeable : - la confiance et l'argent firent défaut ; – et douze années d'efforts furent englouties dans le gouffre du néant , faute de manifestation suffisante.
 * "Mr. Joseph Pline, patented in June 1855, a mixed aeroplane system, of which I may say a few words, had made the plan - as the name of his device indicates - the basis of a system absolutely different from all those who have the aerostat as a starting point... He proposed to build a steerable apparatus: - trust and money were lacking; - and twelve years of effort were engulfed in the abyss of nothingness, for lack of sufficient demonstration".
 * Aviation ou Navigation aérienne (p. 167) by Guillaume Joseph Gabriel de LA LANDELLE; Paris, 1863.
 * I found a "snippet view" of Gothenburg Studies in English, Volume 7 (1958) p. 229:
 * Pline's design was presented at the Exposition Universelle in Paris in 1855, and an abstract of his patent specification was printed in the catalogue of the exhibition (off - print in the library of the Musée de l'Air, Paris), but it appears to have been too impracticable to have been widely noticed.
 * Apologies for the rubbish translation, perhaps someone else can do better... Alansplodge (talk) 12:05, 4 May 2021 (UTC)
 * I think that the word plan in the first quotation refers back to the plan incliné ("inclined plane") mentioned in the preceding paragraph – where "plane" simply means a flat surface. My attempt at an (also not superb) translation: "Mr. Joseph Pline, who had, in June 1855, obtained a patent for a mixed aeroplane system, of which I may say a few words, had made the plane – as the name of his device indicates – the base of a system ...". --Lambiam 15:55, 4 May 2021 (UTC)
 * The 1855 Exposition Universelle official catalogue is here if anyone has time to wade through it. Alansplodge (talk) 12:29, 4 May 2021 (UTC)
 * I've done several searches of the text form of that and can't find anything pertinent. Andy Mabbett ( Pigsonthewing ); Talk to Andy; Andy's edits 15:22, 4 May 2021 (UTC)
 * (ec) I've found several references that indicate that the paper in question was actually a patent application (brevet in French). This may be as close as we can get, No.554, 12 June 1855, although this description only mentions appareil aéronautique. And this may contain direct quotes from the patent: la notion de forme plane par opposition à la notion d'aérostat ordinaire sphérique — "the notion of a plane form in contrast to the notion of the ordinary spherical aerostat" (a balloon). --Wrongfilter (talk) 12:12, 4 May 2021 (UTC)

Further searching has thrown up a mention of. Google Books only has a preview; IA has nothing. I've requested a copy at WP:REX. Andy Mabbett ( Pigsonthewing ); Talk to Andy; Andy's edits 15:34, 4 May 2021 (UTC)

There is also a book of which I only see snippets, but I think that I have pieced together an essential sentence from the description of the invention in the patent: D'après cette comparaison des différences qui existent entre la forme d'un navire aéroplane et celle d'un aérostat ordinaire, on comprend que cette forme plane, horizontale et tranchante puisse être entraînée dans une direction voulue par des hélices ou organes propulseurs, avec beaucoup plus de facilité que les aérostats sphériques ou cylindroconiques dont la forme n'a aucune analogie avec la fonction que nous cherchons à leur faire remplir. Pline contrasts his aéro plane  vessel with an ordinary aéro stat , which makes me believe that -plane was meant to be in opposition to the staticity of -stat. Monsieur Gilbert seems equally tempted to believe this. After revealing that (according to an 18th-century etymologist) the component -stat signifies "to remain stationary", he writes on page 118, On serait tenté alors d'opposer plane du verbe planer, qui signifierait «&thinsp;en planant comme les oiseaux&thinsp;». (One would thus be tempted to see an opposition of -plane from the verb planer, which would signify "gliding like birds". However, the author continues by pointing out that this interpretation can be countered by objections of two different orders. What these are, is hidden behind the veil of GBS. But I find a connection with the (attested) Ancient Greek adjective ἀερόπλανος not implausible; in writing navire aéroplane, Pline also uses his neologism as an adjective. There is no direct connection between Ancient Greek πλάνος (cognate with "planet") and the French verb planer and Latin planus, except that both may ultimately stem from a Proto-Indo-European root pleh₂-. --Lambiam 17:04, 4 May 2021 (UTC)


 * By various dark arts, I have been able to wring out a few more sentences from Monsieur Gilbert's book...
 * "Cette interprétation peut être contrebattue par des objections de deux ordres. D'abord l'intention de signification du créateur ne semble pas avoir été celle - là; ensuite pourquoi l'élément plane aurait - il pris la forme avec un e plutôt que la forme sans e comme aérostat. En faveur de la thèse de l'élément d'origine verbale, Portier avance les éléments graphe, vore, fère, ou phore comme dans planophore. De telles dérivations suffixales sont courantes dans les vocabulaires scientifiques et techniques. En faveur du second élément à caractère nominal, on pourrait invoquer une forme féminine résultant du rapport de signification avec forme dans le texte du brevet (la marque du genre masculin du signe dans sa totalité résultant de..."
 * That's all folks! Alansplodge (talk) 22:46, 4 May 2021 (UTC)


 * The OED says aeroplane was "formed within English by compounding; partly modelled on a French lexical item". From aero (of, from, or to do with, the air) and plane (a flat surface). DuncanHill (talk) 22:55, 4 May 2021 (UTC)
 * Which squares with what Etymology Online says. ←Baseball Bugs What's up, Doc? carrots→ 23:55, 4 May 2021 (UTC)
 * Then I'd really want to know what that "French lexical item" was. --Lambiam 06:17, 5 May 2021 (UTC)


 * From the continuation revealed by the dark arts, I see that I misinterpreted the preceding sentence. Given that Pline explains the superiority of his invention as deriving from its "forme plane", Gilbert surmises that one might be tempted to oppose the theory (which he may have mentioned in an earlier passage) that plane refers to the action of planer. But, says Gilbert, if it comes from the forme plane (in which the French adjective plan ("flat") has an $\langlee\rangle$ because forme is a feminine noun), there should have been no $\langlee\rangle$ in the masculine aéroplane, just like aérostat has no $\langlee\rangle$. Furthermore, Gilbert continues, one Portier has pointed out that suffixes derived from verbs often end on $\langlee\rangle$. (Of the latter's examples, I think planophore is interesting, because -phore is unambiguously derived from the Ancient Greek suffix -φορος.) Clearly, the etymology of aéroplane has been widely discussed, and it seems that Gilbert prefers derivation from the verb planer. As far as I can see, Gilbert does not consider the Greek theory. I see no argument for dismissing it out of hand; I think it deserves serious consideration as being at least one possible explanation for Pline's choice of his neologism. I do not know in which edition of the Great Scott the word ἀερόπλανος first appeared, but it was included in the 1855 edition, and would not have been hard to find for someone with an elementary understanding of the Greek alphabet. Interestingly, in the earliest use of French aérodrome, from ἀερόδρομος, a synonym of ἀερόπλανος, it referred to a flying machine, "l'aérodrome du professeur Lengley". --Lambiam 07:23, 5 May 2021 (UTC)
 * See Langley Aerodrome. Dolphin ( t ) 08:15, 5 May 2021 (UTC)