Inverse Square Laws

Manipulate[Show[{Graphics3D[{Point[{0,0,0}],Line[{{0,0,0},radius{ Cos[#[[1]]] Sin[#[[2]]], Sin[#[[1]]] Sin[#[[2]]], Cos[#[[2]]]}}]&/@Tuples[{π/3,2π/3},2],Opacity[.3],Sphere[{0,0,0},1]}],Table[ParametricPlot3D[{r Cos[θ] Sin[ϕ],r Sin[θ] Sin[ϕ],r Cos[ϕ]},{θ,π/3,2π/3},{ϕ,π/3,2π/3},Mesh->{r-1,r-1},PlotStyle->{Opacity[.7]},PerformanceGoal->"Speed"],{r,1,radius}]},PlotRange->All,Boxed->False,ViewPoint->{2.7550229340996077`,-1.2783201504632618`,1.4918935034059142`},ViewVertical->{0.3754558387166779`,0.14865676602154548`,1.2639319106668794`},ImageSize->{500,400}],{{radius,2},0,10,1,Appearance->"Labeled"}]

CAPTION

Gravity, electrostatic force, and luminosity are inversely proportional to the square of the distance. This Demonstration gives an idea of why: an area projected from the center of a sphere grows proportionately to the square of the distance.

THIS NOTEBOOK IS THE SOURCE CODE FROM

"Inverse Square Laws" from the Wolfram Demonstrations Project
 http://demonstrations.wolfram.com/InverseSquareLaws/

Contributed by: Enrique Zeleny V.

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