Talk:Sphericity

message: On this page - http://en.wikipedia.org/wiki/Sphericity...
The equation provided for the volume of a hemisphere produces a value half the value of the equation provided for the volume of a sphere, but the equation for the surface area of a hemisphere produces a value 3/4ths the value of the equation for the surface area of a sphere. Both should be half. This problem can also be seen by thinking of the area formula as the derivative of the volume formula. That's the case for the formulas provided for the sphere but not for the formulas provided for the hemisphere.
Gregory A. Miller
University of Illinois at Urbana-Champaign  —Preceding unsigned comment added by 74.134.248.240 (talk) 17:51, 4 November 2007 (UTC)
thread_title:  Error in formula for a hemisphere? 

message: The statistical part is very bad and should probably just be removed. This talks about very specific sphericity.  —Preceding unsigned comment added by 142.3.103.20 (talk) 01:54, 18 November 2009 (UTC)
thread_title:  Statistical Part 

message: Is there an alternate definition applicable to bodies that have well-defined volume (and finite convex hull) but not well-defined surface area?  —Tamfang (talk) 20:16, 24 December 2011 (UTC)
thread_title:  fractals? 

message: The examples given include "ideal cone (h=2√2r)", "ideal cylinder (h=2r)", "ideal torus (R=r)". What's ideal about these arbitrary choices of aspect ratio? —Tamfang (talk) 23:10, 20 May 2012 (UTC)
replies: text: Perhaps they are the values which maximize sphericity?--Salix (talk): 08:06, 21 May 2012 (UTC)
thread_title:  ideal cone 

message: The link at the bottom of the page:
  Grain Morphology: Roundness, Surface Features, and Sphericity of Grains
  http://people.uncw.edu/dockal/gly312/grains/grains.htm
Is broken... Edwardando (talk) 15:01, 10 September 2014 (UTC)
thread_title:  Link broken 

message: Over on Talk:Roundness (geology)#Merge with Sphericity scale, that withdrawn merge proposal led to the proposal for a new merge between Sphericity and Sphericity scale. Given the unreferenced stub at Sphericity scale, I support the idea of merging it here. Perhaps continue the discussion here. Klbrain (talk) 12:31, 12 June 2018 (UTC)
thread_title:  Merge proposal 

message: The following are the formulas for sphericities of Platonic solids with rational denominators: 
Tetrahedron:  \Psi{=}\frac{\sqrt[6]{432\pi^2}}{6}  
Cube:  \Psi{=}\frac{\sqrt[3]{36\pi}}{6}  
Octahedron:  \Psi{=}\frac{\sqrt[6]{27\pi^2}}{3}  
Dodecahedron:  \Psi{=}\frac{\sqrt[6]{21060000\pi^2+9396000\sqrt{5}\pi^2}}{30}  
Icosahedron:  \Psi{=}\frac{\sqrt[6]{25380000\pi^2+11340000\sqrt{5}\pi^2}}{30}  
—Jencie Nasino (talk) 05:37, 22 July 2019 (UTC)
thread_title:  Formulas for sphericities of Platonic solids with rational denominators 

message: I'm confused by this.  Is this talking about molecules, atoms, hadrons, leptons, quarks, bosons, rishons, etc.?  Or a mathematical abstraction occupying a single point in space?  The latter would necessarily have zero surface area and zero volume, so the ratio would be 0 : 0, which is somewhat meaningless.  If it's talking about particles in chemistry/physics, I can't see why the definition should be restricted to these.  Furthermore, the Sphericity of common objects section doesn't seem to be talking about particles in either of these senses, so it must be some other definition I haven't come across.  Can anyone shed light? — Smjg (talk) 23:17, 17 July 2023 (UTC)
replies: text: You are trying to make it too complicated. In colloqiual English, a particle is a small piece of matter. A dust particle. A particle of food. A piece of stuff. A thing. See :Wikt:Particle, definition 1. —David Eppstein (talk) 00:28, 18 July 2023 (UTC)
replies: text: Why a small piece of matter in particular?  What is the sphericity of a medium-sized or large piece of matter, if not the same?  What is the sphericity of a geometric shape (which may not have a definite size or be made of matter), which the article goes on to talk about? — Smjg (talk) 12:10, 18 July 2023 (UTC)
replies: text: I don't know why whoever chose that word did so. I would think sphericity would be more relevant for ball bearings, bowling balls, etc., which might be a bit too large to call particles. I'd be open to rewording. —David Eppstein (talk) 17:26, 18 July 2023 (UTC)
replies: text: Whoever chose that wording was apparently following the cited reference, whose abstract refers to "the volume, shape, and roundness of sedimentary quartz particles." I agree that a rewording is in order. Perhaps we should change "particle" to "object." Doctor Whom (talk) 14:44, 20 July 2023 (UTC)
replies: text: I thought myself "object" would be better.  I haven't changed the sentence about Hakon Wadell's definition, as I would guess he defined it in terms of particles, so we may need to think a bit more about how to link talking about particles to talking about objects or geometric shapes more generally. — Smjg (talk) 16:23, 20 July 2023 (UTC)
thread_title:  Particle?