{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.topic/1","content_sha256":"58178bae7ac7045c9a570ade45e12d13f9da8ab59a23bd7f6cf6bda7e32550bd","created":"2026-10-03T07:17:51Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":[],"salt":"bb0526d13a5d76b843f5be9e33ab877946964bf1c675ac05755b251aa0b20703","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"topic"},"content":{"external_id":"grav.problem-of-time","field":"grav","n":"1","review_cite":"C. J. Isham, Canonical quantum gravity and the problem of time, arXiv:gr-qc/9210011, 1992","review_link":"https://arxiv.org/abs/gr-qc/9210011","review_verified":"true","summary":"In quantum mechanics time is an external clock, but in general relativity time is part of the dynamical geometry, and the basic quantum equation for the universe, the Wheeler-DeWitt equation, contains no time at all. How ordinary time-dependent physics emerges from a timeless description is not settled.","title":"The problem of time in quantum gravity","topic_ref":null,"why":"Without a resolution there is no agreed meaning for probability and evolution in a quantum theory of gravity or of the whole universe."},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"266bbe8da17b18c5bdcf2f6e3eb994ed918fe1decf73bbef01ce81ac54cc2474","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"73d38009b9357477f049056526ae27dbc869d9d36bcfe548fdc801b08e19398f","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"OQSZChAf4J-cjoUnF7x_riodjZf4wwwgul3m7JVnxKXzucJvuYNJeCP0BNZIAU2xU0zfSMh5Eo_jgIaTBtXgCg"},"schema":"pubphys.envelope/1"},"record_hash":"266bbe8da17b18c5bdcf2f6e3eb994ed918fe1decf73bbef01ce81ac54cc2474","leaf_index":232}