Talk:Mean radius

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Non-spherical vs. non-spheroidal[edit]

The article claimed that: "For a non-spherical object, the mean radius (denoted R or r) is defined as the radius of the sphere that would enclose the same volume as the object." It then went on to give formulae for oblate spheroid and ellipsoids, which are not spherical in most cases. The two definitions appear to contradict each other. Praemonitus (talk) 14:26, 18 June 2024 (UTC)[reply]

@Praemonitus: There's clearly some misunderstanding, because there is only one definition. In the first paragraph, it distinguishes between the case of a sphere (which is trivial, see the last sentence), and every other shape. The formulae below apply to the special case of ellipsoids (either oblate spheroids or triaxial ellipsoids), for which the mean radius as defined before can actually be easily calculated. The dimensions (2 or 3 axes) for irregularly shaped objects are usually those of the ellipsoid with the same volume (because that's actually useful), motivating this definition of mean radius. Renerpho (talk) 16:13, 18 June 2024 (UTC)[reply]

By the way, the wording reflects the reference. Ref.1 ("Distorted, nonspherical transiting planets...") singles out non-spherical objects, and so did I. As I said, the case of the sphere is really trivial (its radius is defined as the radius). Renerpho (talk) 17:30, 18 June 2024 (UTC)[reply]

@Praemonitus: I edited the article, to hopefully clarify what is the definition, what motivates it, and how it is used in practice. I'm sure this can be improved much further, but hopefully it's less confusing now. Renerpho (talk) 16:32, 18 June 2024 (UTC)[reply]