{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"3648daedf58c133774820deb6a7006afdf023cbeb0e1631219a6d1af58a2ce29","created":"2026-10-03T07:18:10Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011","c1f790f8de35d3d5f60c9a6639d7ec2e82b87f301b7e81cc6890231b220c7bef"],"salt":"73aeb00a2c4a404d8dc43ad6aab89911e51c9bec97d791e97b30e2dd2f5d2d51","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"qi.gravity-quantum.superposed-source-gravity","kind":"well-posed","literature_status":"open","n":"1","parents":[{"note":"","parent_revision":"c1f790f8de35d3d5f60c9a6639d7ec2e82b87f301b7e81cc6890231b220c7bef","relation":"special_case"}],"plain":"Gravity has been measured from masses of about 90 milligrams, but never from an object that is itself in a superposition of two places. Doing so would show whether a quantum source pulls on a probe through its average position or through each branch separately.","posed_since":"","precise":"Prepare a source mass $M$ in a spatial superposition of separation $\\Delta x$ and measure a probe's response that distinguishes a field sourced by the expectation value $\\langle T_{00}\\rangle$ (Moller-Rosenfeld semiclassical gravity) from a branch-correlated field, at force scale $\\sim G M m_{\\mathrm{probe}} \\Delta x / d^3$. Required: source masses small enough to superpose ($M <\\sim 1e-11\\,\\mathrm{g}$) and probe force sensitivity at that scale.","problem_ref":null,"references":"","settled_by":"A probe measurement whose outcome statistics are correlated with the source branch (quantum) or follow the mean field (semiclassical).","status_note":"Page and Geilker (1981) excluded the simplest mean-field model using a classically randomized source; no experiment has used a source in a coherent spatial superposition.","title":"Measure the gravity of a mass that is in 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