From the Online Etymology Dictionary on ‘earth’:
O.E. eorþe “ground, soil, dry land,” also used (along with middangeard) for “the (material) world” (as opposed to the heavens or the underworld), from P.Gmc. *ertho (cf. O.Fris. erthe “earth,” O.S. ertha, O.N. jörð, M.Du. eerde, Du. aarde, O.H.G. erda, Ger. Erde, Goth. airþa), from PIE base *er- “earth, ground” (cf. M.Ir. -ert “earth”). The earth considered as a planet was so called from c.1400.
Perhaps when I’m feeling less intellectually lazy, I’ll try to figure out the translated meaning of the author’s actually used word. But for now, I still don’t see much about ‘earth’ that requires it to mean specifically this planet or even this “universe” (that’s an odd term if our universe is more like one among many connected universes in an even larger multiverse… making the multiverse totality the real “universe”/“earth”/material world perhaps.) Why wouldn’t “earth,” what philosophers used to consider a primary building block of the material world, not our planet or solar system or galaxy or, presumably, post-Big Bang universe, just apply to the “dust” which is transient, material existence?
I happen to think it’s most likely that the Garden was on our planet, but I do think there’s “doxastic wiggle room” here. Thank you for providing that source, though. Anyone know what the original Scripture language for these passages meant by “heaven” and “earth”? I mean, wouldn’t excluding multiverses from “earth” make them into heaven, especially since anything pre-Big Bang would better qualify as “in the beginning”?