alt Hacker NewsThat seems to be milking the explanation for all it's worth!
The short answer being that if something is radiating out 3-dimensinally in all directions, then at a given distance, r, that thing (light/whatever) is being spread out over an area equal to the surface area of a sphere of that radius, which is 4 x pi x r^2, i.e. the intensity is inversely proportional to the square of the distance (r^2).
Exactly. The marble metaphor should've been enough to get the point across.
Big fan of lcamtuf's writing (I think it's the only 'subscribe to my newsletter' offer I've ever actually clicked) but this one seemed a bit overcooked.