Q2 is just an id, probably one shouldn't interpret too much into it except that it defines an entity. Regarding the diameter, probably it depends how you define

Q2 is just an id, probably one shouldn't interpret too much into it except that it defines an entity. Regarding the diameter, probably it depends how you define it. For instance according to Wikipedia one can generalize it as sup { d(x,y) }, seems legitimate to me although Wikidata's referenced diameter definition (P2386) isn't that general, probably it should be updated... But to be fair, Earth (Q2) has the shape (P1419) oblate spheroid (Q3241540) under sourcing circumstances (P1480) approximation (Q27058) :-) To me Wikidata (and similar projects like OSM) shine because they tend to have so many details.