{
  "slug": "the-visitor-gravity-could-not-fit",
  "title": "The Visitor Gravity Could Not Fit",
  "href": "/strata/the-visitor-gravity-could-not-fit/",
  "field": "astronomy",
  "claim": {
    "statement": "Here we report the detection, at 30σ significance, of non-gravitational acceleration in the motion of ‘Oumuamua.",
    "claimants": "Marco Micheli, Davide Farnocchia, Karen J. Meech, Marc W. Buie, Olivier R. Hainaut, Dina Prialnik, Norbert Schörghofer, Harold A. Weaver, Paul W. Chodas, Jan T. Kleyna, Robert Weryk, Richard J. Wainscoat, Harald Ebeling, Jacqueline V. Keane, Kenneth C. Chambers, Detlef Koschny, Anastassios E. Petropoulos",
    "citation": "Marco Micheli, Davide Farnocchia, Karen J. Meech, Marc W. Buie, Olivier R. Hainaut, Dina Prialnik, Norbert Schörghofer, Harold A. Weaver, Paul W. Chodas, Jan T. Kleyna, Robert Weryk, Richard J. Wainscoat, Harald Ebeling, Jacqueline V. Keane, Kenneth C. Chambers, Detlef Koschny, Anastassios E. Petropoulos. Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua). Nature 559, 223-226 (2018). DOI 10.1038/s41586-018-0254-4.",
    "year": 2018,
    "headline_as_printed": "A₁ = (4.92 ± 0.16) × 10⁻⁶ m s⁻²; about 30σ"
  },
  "records": [
    {
      "role": "claimant-data",
      "name": "observations.json",
      "file": "observations.json",
      "url": "https://media.springernature.com/original/springer-static/esm/art%3A10.1038%2Fs41586-018-0254-4/MediaObjects/41586_2018_254_MOESM2_ESM.xlsx",
      "licence": "Numerical factual extract; source publication all rights reserved; no open licence claimed for source workbook",
      "licence_url": "https://support.nature.com/en/support/solutions/articles/6000080095-author-copyrights-information",
      "retrieved": "2026-09-22",
      "sha256": "9f3b64dfbf513ae4ec3034232dfedb8c2e053f5c6d9c322453aa04bea72c5e17",
      "units": 216
    },
    {
      "role": "claimant-data",
      "name": "ed-table-1.json",
      "file": "ed-table-1.json",
      "url": "https://lweb.cfa.harvard.edu/~loeb/micheli.pdf",
      "licence": "Numerical factual transcription of Extended Data Table 1; source publication all rights reserved; no open licence claimed",
      "licence_url": "https://support.nature.com/en/support/solutions/articles/6000080095-author-copyrights-information",
      "retrieved": "2026-09-22",
      "units": 53,
      "sha256": "77118ec70bf2d4b35b91be70343afa7b98072038738ecafa8959feb3d097a1d2"
    },
    {
      "role": "control-data",
      "name": "geometry.json",
      "file": "geometry.json",
      "url": "https://ssd.jpl.nasa.gov/api/horizons.api",
      "licence": "Derived numerical observer geometry; NASA/JPL-Caltech credited; no open licence claimed for website material",
      "licence_url": "https://ssd-api.jpl.nasa.gov/",
      "retrieved": "2026-09-22",
      "sha256": "82a34bece2320a7d2c6d76802cccad2481e00601a912b0e3ac6639e578debed8",
      "units": 216
    },
    {
      "role": "reference",
      "name": "ephemeris.json",
      "file": "ephemeris.json",
      "url": "https://ssd.jpl.nasa.gov/api/horizons.api",
      "licence": "Numerical factual ephemeris extract; NASA/JPL-Caltech credited; API fair-use conditions",
      "licence_url": "https://ssd-api.jpl.nasa.gov/",
      "retrieved": "2026-09-22",
      "sha256": "d39019c32de3aacfcbe3ce546edd20b4446ac9f8d431f037a8e667de2d94fa26",
      "units": 9207
    },
    {
      "role": "reference",
      "name": "hst-transcription.json",
      "file": "hst-transcription.json",
      "url": "https://lweb.cfa.harvard.edu/~loeb/micheli.pdf",
      "licence": "Numerical factual transcription; source all rights reserved",
      "licence_url": "https://support.nature.com/en/support/solutions/articles/6000080095-author-copyrights-information",
      "retrieved": "2026-09-22",
      "sha256": "102c221495eb0d648c11e737919577de918e699992e585d8422bc0be9647f0f7",
      "units": 30
    },
    {
      "role": "reference",
      "name": "experiments.json",
      "file": "experiments.json",
      "url": "https://artwaste.land/strata/the-visitor-gravity-could-not-fit/engine.js",
      "licence": "Original computations by Artificial Wasteland",
      "licence_url": "https://artwaste.land/strata/the-visitor-gravity-could-not-fit/NOTICE.txt",
      "retrieved": "2026-09-22",
      "sha256": "93087ff428fd0cddbb3f645135e37dfc82832dcf87bdaf051588ea89fbd2480b",
      "units": 63
    },
    {
      "role": "reference",
      "name": "trajectory-reference.json",
      "file": "trajectory-reference.json",
      "url": "https://artwaste.land/checks/research/the-visitor-gravity-could-not-fit/crosscheck.py",
      "licence": "Original independent computations using SciPy",
      "licence_url": "https://artwaste.land/strata/the-visitor-gravity-could-not-fit/NOTICE.txt",
      "retrieved": "2026-09-22",
      "sha256": "168e718bf4a5c39e87d4cf75e1048ea91251ab74be1ca613b9e28aab49fa079c",
      "units": 16
    },
    {
      "role": "reference",
      "name": "acquisition.json",
      "file": "acquisition.json",
      "url": "https://ssd.jpl.nasa.gov/api/horizons.api",
      "licence": "Original request and checksum log",
      "licence_url": "https://ssd-api.jpl.nasa.gov/",
      "retrieved": "2026-09-22",
      "sha256": "c8cd4dcf8568aa05060cbdc89ce45789bd509b2c1b4c40a90d701842ea263565",
      "units": 135
    },
    {
      "role": "reference",
      "name": "source-checks.json",
      "file": "source-checks.json",
      "url": "https://artwaste.land/strata/the-visitor-gravity-could-not-fit/NOTICE.txt",
      "licence": "Original source retrieval metadata",
      "licence_url": "https://artwaste.land/strata/the-visitor-gravity-could-not-fit/NOTICE.txt",
      "retrieved": "2026-09-23",
      "sha256": "c6fa1349c2285df0c520afd9f97e9ba1758120ef2490d772148252d99d602d03",
      "units": 21
    },
    {
      "role": "reference",
      "name": "vector-labels.json",
      "file": "vector-labels.json",
      "url": "https://ssd.jpl.nasa.gov/api/horizons.api",
      "licence": "Factual source version identifiers; NASA/JPL-Caltech credited",
      "licence_url": "https://ssd-api.jpl.nasa.gov/",
      "retrieved": "2026-09-22",
      "sha256": "7da9fadcb780a9e3d0d4819fdd2560356f0ad740f213e91ac95e19d62bb23adf",
      "units": 27
    }
  ],
  "anchor": {
    "what": "The claimants’ fit, refitted: six initial state components plus a radial push A₁(1 au/r)² from the measured positions, with Extended Data Table 1’s printed values for the team’s 53 ground rows",
    "expected": "A₁ = (4.92 ± 0.16) × 10⁻⁶ m s⁻², about 30σ; Table 1 χ² 1031 for gravity alone and 81 for 1/r²; ten gravity-only positions beyond 5σ and 25 beyond 3σ; 207 positions",
    "computed": "4.919 ± 0.160 × 10⁻⁶ m/s², 30.76σ. χ² 1028.97 for gravity alone, 82.30 with the push; 208 positions. Rounded to the printed digits: 4.92 ± 0.16, the same as the paper.",
    "agrees": true,
    "printed_digits_agree": true,
    "tolerance": "A₁ and σ(A₁) must round to the printed 4.92 and 0.16; the envelope fixed before fitting (|A₁ − 4.92| ≤ 0.05, |σ − 0.16| ≤ 0.02, 29 ≤ A₁/σ ≤ 34) must hold; Table 1 χ² within 3 of print. The fit counts 208 positions against the printed 207; the extra position cannot be identified from what is published.",
    "workbook_replay": "4.959 ± 0.159 × 10⁻⁶ m/s²; 31.12σ; χ² 90.48; 208 positions."
  },
  "control": {
    "name": "Gravity-only orbit refitted to the same positions with the same weights, against the radial-push orbit; both with all six starting components free",
    "citation": "Marco Micheli, Davide Farnocchia, Karen J. Meech, Marc W. Buie, Olivier R. Hainaut, Dina Prialnik, Norbert Schörghofer, Harold A. Weaver, Paul W. Chodas, Jan T. Kleyna, Robert Weryk, Richard J. Wainscoat, Harald Ebeling, Jacqueline V. Keane, Kenneth C. Chambers, Detlef Koschny, Anastassios E. Petropoulos. Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua). Nature 559, 223-226 (2018). DOI 10.1038/s41586-018-0254-4. Figure 2, Table 1, main text and Methods.",
    "computed": "Gravity alone χ² 1028.97; with the push χ² 82.30; 10 positions beyond 5σ and 25 beyond 3σ under gravity alone; 208 positions.",
    "as_printed": "Gravity alone χ² 1031; inverse-square push χ² 81; ten positions beyond 5σ and 25 beyond 3σ under gravity alone; 207 positions."
  },
  "power": {
    "grade": "A-injection",
    "planted": "4.92 × 10⁻⁶ m/s² added by physical forward propagation to a copy of the actual measured positions, and again onto real residuals transferred to a gravity-only trajectory; repeated in each of the claimants’ nine robustness subsets.",
    "recovered": "CONTROL CAN CONFIRM. Before 4.919, after 9.839: recovered increment 4.920, planted 4.920. Transferred baseline 0.000; planted there, 4.920 ± 0.160, 30.77σ. All accelerations in × 10⁻⁶ m/s².",
    "verdict": "the control COULD have confirmed the claim on the full arc (CONTROL CAN CONFIRM, expected 30.77σ at the claimed size); in the two half-arc subsets the claimed push would be expected to reach only 3.07σ and 3.37σ, below this page’s 5σ bar, so the page says INCONCLUSIVE there, and adds that with unit scatter a half carrying the full push would reach 5σ 2.7% and 5.1% of the time"
  },
  "null_through_claimant_method": {
    "applicable": true,
    "what": "Conditional nulls with the actual epochs, stations and covariance, fitted by the same two orbit fits as the anchor: Gaussian errors, and fitted residuals with one random sign per station and UTC night.",
    "result": "24 trials, seeds 1 through 24: 0 reached |A₁/σ| ≥ 30; largest |A₁/σ| = 3.57; standard deviation of A₁/σ = 1.18. 24 trials, seeds 1 through 24: 0 reached |A₁/σ| ≥ 30; largest |A₁/σ| = 1.11; standard deviation of A₁/σ = 0.66."
  },
  "verdict": {
    "category": "VINDICATED",
    "as_of": "2026-09-22",
    "sources": [
      "Marco Micheli, Davide Farnocchia, Karen J. Meech, Marc W. Buie, Olivier R. Hainaut, Dina Prialnik, Norbert Schörghofer, Harold A. Weaver, Paul W. Chodas, Jan T. Kleyna, Robert Weryk, Richard J. Wainscoat, Harald Ebeling, Jacqueline V. Keane, Kenneth C. Chambers, Detlef Koschny, Anastassios E. Petropoulos. Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua). Nature 559, 223-226 (2018). DOI 10.1038/s41586-018-0254-4.",
      "Federico Spada. Revisiting the trajectory of the interstellar object ‘Oumuamua: preference for a radially directed non-gravitational acceleration? arXiv:2304.06964v1, 14 April 2023. DOI 10.48550/arXiv.2304.06964. Preprint.",
      "David Jewitt and Darryl Z. Seligman. The Interstellar Interlopers. Annual Review of Astronomy and Astrophysics 61, 197-236 (2023). DOI 10.1146/annurev-astro-071221-054221; arXiv:2209.08182v1.",
      "D. Farnocchia, O. R. Hainaut, D. Z. Seligman, R. Weryk, L. A. M. Benner, M. Brozović, L. Denneau, A. Galád, J. D. Giorgini, K. Hornoch, M. Micheli, S. P. Naidu, R. S. Park, P. Pravec and R. J. Wainscoat. Non-gravitational acceleration indicative of cometary activity of near-Earth object. Nature Astronomy 10, 1283-1291 (2026), published 10 July 2026. DOI 10.1038/s41550-026-02913-7."
    ],
    "would_change": "A reproducible re-reduction of the original images, or a documented correction to the positions, timing, observer geometry or error model, that removes the acceleration across the full arc and also accounts for the independent reanalyses, would change this verdict. A better orbit fit alone would not establish any particular cause."
  },
  "decided_by": "analysis",
  "years_to_decision": 0,
  "choices": [
    {
      "id": "model",
      "label": "Dynamical model",
      "options": [
        "gravity",
        "radial"
      ],
      "default": "radial",
      "affects": [
        "residuals",
        "chi2",
        "parameter count"
      ],
      "inert": false
    },
    {
      "id": "law",
      "label": "Distance law of the push, exponent k in (1 au/r)^k",
      "options": [
        2,
        1,
        0,
        3
      ],
      "default": 2,
      "affects": [
        "A",
        "chi2"
      ],
      "inert": false
    },
    {
      "id": "dataset",
      "label": "Input positions",
      "options": [
        "printed",
        "workbook"
      ],
      "default": "printed",
      "affects": [
        "A",
        "sigma",
        "chi2"
      ],
      "inert": false
    },
    {
      "id": "arc",
      "label": "Observation set (the claimants’ robustness tests)",
      "options": [
        "full",
        "after-oct25",
        "late",
        "early",
        "before-dec1",
        "hst-ogs",
        "hst-cfht",
        "hst-vlt",
        "ground"
      ],
      "default": "full",
      "affects": [
        "count",
        "A",
        "sigma",
        "injection recovery"
      ],
      "inert": false
    },
    {
      "id": "floor",
      "label": "Positional uncertainty floor in arcseconds",
      "options": [
        0.05,
        0.2,
        1
      ],
      "default": 0.05,
      "affects": [
        "covariance",
        "formal significance",
        "power"
      ],
      "inert": false
    },
    {
      "id": "plant",
      "label": "Planted increment in claimed sizes",
      "options": [
        1,
        0,
        -1
      ],
      "default": 1,
      "affects": [
        "input coordinates",
        "recovered increment"
      ],
      "inert": false
    },
    {
      "id": "units",
      "label": "Residual units",
      "options": [
        "normalized",
        "arcsec"
      ],
      "default": "normalized",
      "affects": [
        "plot ordinates"
      ],
      "inert": false
    },
    {
      "id": "noise",
      "label": "Conditional null model",
      "options": [
        "gaussian",
        "blocks"
      ],
      "default": "gaussian",
      "affects": [
        "generated positions",
        "fitted A"
      ],
      "inert": false
    },
    {
      "id": "seed",
      "label": "Conditional null seed",
      "options": [
        1,
        999999
      ],
      "default": 1,
      "affects": [
        "generated positions",
        "fitted A"
      ],
      "inert": false
    },
    {
      "id": "spadaSeed",
      "label": "Seed for the noise added to six 19 October positions",
      "options": [
        1,
        999999
      ],
      "default": 1,
      "affects": [
        "noised positions",
        "residual scatter"
      ],
      "inert": false
    },
    {
      "id": "denominator",
      "label": "Katz night display",
      "options": [
        "arcsec",
        "normalized",
        "shift"
      ],
      "default": "arcsec",
      "affects": [
        "comparison table values"
      ],
      "inert": false
    }
  ],
  "headline": "An outward acceleration fits the observed arc; its physical cause remains open.",
  "novelty": "we searched the Artificial Wasteland corpus, web search for interactive orbit fits and injection recovery, arXiv reanalyses, and Federico Spada’s public orbit_finder repository on 2026-09-22 and did not find a public reader-operated page combining a claimant-astrometry orbit refit, recovery of an added acceleration on those observations, and a comparison of power across shortened observation arcs.",
  "further_result": "This page’s result: planted at the claimed size, the push would be expected to reach 30.77σ on the full arc, 16.19σ after 25 October, and only 3.07σ before 15 November and 3.37σ after it. Those two halves report INCONCLUSIVE and INCONCLUSIVE under the stated rule. These are conditional sensitivity calculations, not evidence that the force switched on or off.",
  "ledger": {
    "claim_reproduced": {
      "value": true,
      "assertion": "anchor:printed-digits-from-printed-team-table"
    },
    "control_computed": {
      "value": true,
      "assertion": "control:both-models-free-state"
    },
    "control_can_confirm": {
      "value": true,
      "assertion": "power:planted-4.92-increment-recovered"
    },
    "rendered_figures_asserted": {
      "value": true,
      "assertion": "surface:every-copy-block-and-table"
    },
    "choices_are_live": {
      "value": true,
      "assertion": "choices:each-changes-an-output"
    },
    "planted_fault_caught": {
      "value": true,
      "assertion": "fault:sky-table-clock-observer"
    },
    "refusal_asserted": {
      "value": true,
      "assertion": "refuse:epoch-rank-law-units-selection"
    },
    "provenance_pinned": {
      "value": true,
      "assertion": "provenance:sha256-matches"
    },
    "verdict_dated": {
      "value": true,
      "assertion": "verdict:category-date-sources-printed"
    }
  }
}