{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"a7cdd209d63fa6f907170630e41051407751ac63a7fc351b11693085476ed18f","created":"2026-10-03T07:18:02Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"2d4fbb92c0324a2e3931f51c42273ded3145c98a1332e7cd2bbe505996b7aece","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"cosmo.quantum-cosmology.cosmic-beginning","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"A theorem shows that an expanding universe like ours cannot be extended infinitely into the past using ordinary spacetime. Whether quantum gravity removes that edge or describes a true beginning is unknown.","posed_since":"","precise":"The Borde-Guth-Vilenkin theorem (2003) shows that any spacetime with averaged expansion rate $H_{\\mathrm{avg}} > 0$ along past-directed geodesics is past-incomplete, so eternal inflation alone cannot be past-eternal. Determine what quantum gravity puts at that boundary (no-boundary state, bounce, emergent or quantum creation) in a framework that yields predictions for observable spectra or spatial curvature.","problem_ref":null,"references":"","settled_by":"A quantum-gravity model of the initial state that predicts a measurable signature (spatial curvature, low-multipole CMB features, tensor tilt) later confirmed.","status_note":"","title":"Did time have a beginning, and what came before the hot Big Bang?","topic_ref":"316c65cff3d448b6835a5fe0d3c6263860b268b7d9bf5157ff20e9877ce5ed6e"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"37af2c82ef6a23dc93532e942e600aae0577e8f4cfa135ee1f105d118dd8dd26","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"da707aa6a17f0ad04b87038edb8f8b015c49e671b4a27707bc8b0c3ac62815cf","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"gLUDEzt27juxT1DK5n1uIoc1Njc0MuqZ-8wpLnSUAGRtgJTxeCK06mjf3GGoB-IEzHWMJrwpb2pcf67rJXctCw"},"schema":"pubphys.envelope/1"},"record_hash":"37af2c82ef6a23dc93532e942e600aae0577e8f4cfa135ee1f105d118dd8dd26","leaf_index":1275}