{
  "slug": "the-dust-between-the-stars",
  "title": "The Dust Between the Stars",
  "href": "/strata/the-dust-between-the-stars/",
  "field": "observational cosmology",
  "claim": {
    "statement": "The observed B-mode power spectrum is well fit by a lensed-ΛCDM + tensor theoretical model with tensor-to-scalar ratio r=0.20^{+0.07}_{-0.05}, with r=0 disfavored at 7.0σ.",
    "claimants": "BICEP2 Collaboration, P. A. R. Ade et al.",
    "citation": "BICEP2 Collaboration, P. A. R. Ade et al. (2014). Detection of B-Mode Polarization at Degree Angular Scales by BICEP2. Physical Review Letters 112, 241101. Published 19 June 2014. DOI 10.1103/PhysRevLett.112.241101. Preprint arXiv:1403.3985v3, revised 23 June 2014.",
    "year": 2014,
    "headline_as_printed": "r = 0.20 (+0.07, -0.05), with r = 0 disfavored at 7.0 sigma (arXiv:1403.3985v3 abstract; Section XI.1: L(0)/L(peak) = 2.9e-11, PTE 3.3e-12)"
  },
  "records": [
    {
      "role": "claimant-data",
      "file": "claimant.json",
      "name": "BICEP2 2014 released likelihood for r (direct likelihood, Figure 10 middle panel), normalised to its peak",
      "url": "https://lambda.gsfc.nasa.gov/data/suborbital/BICEP2/B2_3yr_rlikelihood_20140314.txt",
      "upstream_sha256": "e1c21a9b4848ac9a9ac0813400be957c953914916294055005bfa59faaeaf8c6",
      "units": 751,
      "licence": "numerical facts and derived arrays from the cited public release; no explicit data licence found; source acknowledgement included",
      "licence_url": "https://lambda.gsfc.nasa.gov/contact/",
      "retrieved": "2026-09-22",
      "sha256": "1fb09d8e4315f71e5c9e2734db9c6644b61df57d65cade33134fe8b23f9f6d74"
    },
    {
      "role": "reference",
      "file": "published-joint.json",
      "name": "BICEP2/Keck and Planck 2015 released likelihood for r, normalised to its peak; comparison only, never an input",
      "url": "https://lambda.gsfc.nasa.gov/data/suborbital/BICEP2KP/BKP_r_likelihood_20150123.txt",
      "upstream_sha256": "0dde4ee5aa57772201e06f548b08448613408527b651000814b1141342b54354",
      "units": 301,
      "licence": "numerical facts and derived arrays from the cited public release; no explicit data licence found; source acknowledgement included",
      "licence_url": "https://lambda.gsfc.nasa.gov/contact/",
      "retrieved": "2026-09-22",
      "sha256": "3dc66a0682fbb61305fd565f066de0aa6d37167bb2885cca8ed58891d7f099b8"
    },
    {
      "role": "control-data",
      "file": "joint.json",
      "name": "Selected BB bandpowers (six spectra, five bins), noise, fiducial model, correlation and scales of the selected covariance, window-projected tensor, lensing and dust shapes, bandpass kernels",
      "url": "https://lambda.gsfc.nasa.gov/data/suborbital/BICEP2KP/BKP_likelihood_cosmomc_20150131.tgz",
      "upstream_sha256": "64d8c1b0cd90eff9ea702907365260d88f1c7227dd2a88b1464f8bbc21c51802",
      "derived_from_also": [
        {
          "url": "https://lambda.gsfc.nasa.gov/data/suborbital/BICEP2/B2_3yr_camb_planck_withB_uK_20140314.txt",
          "sha256": "96539118cf31286d788927e63b2956e90465906a749edc8ead92c592dde6810b"
        },
        {
          "url": "https://lambda.gsfc.nasa.gov/data/suborbital/BICEP2K/BK_camb_planck_lensed_uK_20150129.txt",
          "sha256": "521c3696ea2a4aa5dda541be231241aad9e62b1bcff392b2ff3adf175364c937"
        }
      ],
      "units": 30,
      "licence": "numerical facts and derived arrays from the cited public release; no explicit data licence found; source acknowledgement included",
      "licence_url": "https://lambda.gsfc.nasa.gov/contact/",
      "retrieved": "2026-09-22",
      "sha256": "c5016a7e0bf02015dcbda387f348671bde448d7eb9f06c72388f2bba4f59658e"
    }
  ],
  "anchor": {
    "what": "The collaboration’s released 2014 likelihood table for r, summarised by the page’s summarizeLikelihood (peak, equal-density 68% interval) and nullTail (sqrt(-2 ln L0/Lpeak)).",
    "expected": "r = 0.20 +0.07 -0.05; r = 0 disfavored at 7.0 sigma",
    "computed": "peak 0.196000; 68% [0.145200, 0.262072]; errors -0.050800 +0.066072; sigma 6.958761; L0/Lmax 3.053407e-11; full-tail PTE 3.4328e-12",
    "agrees": true,
    "tolerance": "Rounding of the printed values: 0.005 in the peak and each error (two decimals), 0.05 in the significance (one decimal). File-level checks: peak within 0.0005 of 0.196 and interval ends within 0.0001 of an independent reading. The printed ratio 2.9e-11 and PTE 3.3e-12 differ from the released table (3.05e-11, 3.4e-12) and are reported, not toleranced."
  },
  "control": {
    "name": "The 2015 BICEP2/Keck and Planck multi-component likelihood (BK150, P217, P353; six BB spectra; bins 1 to 5; Hamimeche-Lewis; dust amplitude and spectral index marginalised with the beta_d prior 1.59 +/- 0.11), reimplemented from the released bandpowers",
    "citation": "BICEP2/Keck and Planck Collaborations, P. A. R. Ade et al. (2015). Joint Analysis of BICEP2/Keck Array and Planck Data. Physical Review Letters 114, 101301. Published 9 March 2015. DOI 10.1103/PhysRevLett.114.101301. Preprint arXiv:1502.00612v2, revised 14 April 2015.",
    "computed": "r peak 0.048000; 68% [0.016135, 0.083718]; 95% endpoint 0.121255; L0/Lmax 0.371843 (half-tail 0.079771); A_d peak 3.20 [2.417, 4.203], A_d = 0 at 5.131 sigma",
    "as_printed": "r = 0.048 +0.035 -0.032; r_0.05 < 0.12 at 95% confidence; L0/Lpeak = 0.38 (8%); A_d = 3.3 +0.9 -0.8 uK^2, zero-to-peak 1.8e-6, 5.1 sigma (arXiv:1502.00612v2 Section III.2)",
    "agrees_with_released_curve": true,
    "gaps_to_released_curve": {
      "peak": 0,
      "low68": 0.000467,
      "high68": 0.000893,
      "upper95": 0.000787,
      "ratio": -0.006647
    }
  },
  "power": {
    "grade": "A-injection",
    "planted": "r = 0.2, the claimed size: 0.2 times the released 2014 tensor-only BB spectrum (r = 0.1 file divided by 0.1), projected through each spectrum’s released bandpower window, added to all six auto and cross spectra of a copy of the observed 2015 joint vector. Noise, fiducial model, covariance, priors, bounds and algorithm unchanged; the same runJoint.",
    "recovered": "peak 0.248000 (from 0.048000); increment 0.200000; 68% [0.191168, 0.309500]; profile statistic 5.050336 (from 1.339317)",
    "verdict": "the control COULD have confirmed the claim: on this observed sky the unchanged likelihood recovers the planted r = 0.2 under the declared rule (peak rise within 0.02 of 0.20, profile statistic at least 3)",
    "scope": "One deterministic addition of expected bandpowers to one observed residual. Not an ensemble power percentage and not a calibrated discovery probability. The 2015 paper’s own r = 0 simulations (median 95% limit r < 0.075) bear on the ensemble question only indirectly and are cited as published context, not recomputed.",
    "negative_control": "The same plant through the same runJoint on a copy of the data with every covariance scale doubled (noise offsets untouched; a test of the rule, not a model of a noisier experiment): increment 0.196000, profile statistic 2.809672, rule not met (inconclusive). The rise is a bias check; the profile statistic is the power half of the rule.",
    "across_second_layer": "6 of 6 paired settings meet the declared recovery rule. Without the plant, the 95% upper endpoint ranges from 0.103 to 0.143; with r = 0.2 added, the fitted peak rises by 0.184 to 0.208 and the profile statistic reaches 3.51 to 6.47. The closest call is BK150 + 353 GHz with the prior centred on 1.30: its rise of 0.184 is 0.004 inside the rule's edge."
  },
  "null_through_claimant_method": {
    "applicable": false,
    "what": "Not applicable. The 2015 correction identified a real foreground, not an excess manufactured from an empty sky, so the question is not how often the 2014 method finds a signal in nothing. A sky without tensor modes still contains lensing, dust and noise, and the 2014 release is a one-dimensional likelihood, not the maps, simulations and pipeline that would be needed to measure how often that method attributes such a sky to r. Pushing invented skies through a new implementation would not be the original procedure, so the page does not report a rate.",
    "result": "Not performed; no rate is reported."
  },
  "verdict": {
    "category": "ARTEFACT",
    "subject": "the attribution of the 2014 excess to primordial gravitational waves near r = 0.2",
    "as_of": "2026-09-22",
    "sources": [
      "BICEP2/Keck and Planck Collaborations, P. A. R. Ade et al. (2015). Joint Analysis of BICEP2/Keck Array and Planck Data. Physical Review Letters 114, 101301. Published 9 March 2015. DOI 10.1103/PhysRevLett.114.101301. Preprint arXiv:1502.00612v2, revised 14 April 2015.",
      "BICEP/Keck Collaboration, P. A. R. Ade et al. (2021). Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season. Physical Review Letters 127, 151301. Published 4 October 2021. DOI 10.1103/PhysRevLett.127.151301. Preprint arXiv:2110.00483v1, 1 October 2021.",
      "Planck Collaboration, R. Adam et al. (2016). Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes. Astronomy and Astrophysics 586, A133. DOI 10.1051/0004-6361/201425034. Preprint arXiv:1409.5738v1, 19 September 2014; accepted version arXiv:1409.5738v2, 8 December 2014, whose abstract is quoted.",
      "BICEP/Keck Collaboration, P. A. R. Ade et al. (2026). BICEP/Keck. XX. Component-separated Maps of the Polarized Cosmic Microwave Background and Thermal Dust Emission Using Planck and BICEP/Keck Observations through the 2018 Observing Season. Astrophysical Journal 999(1), 89. Published 25 February 2026. DOI 10.3847/1538-4357/ae3e53. Preprint arXiv:2509.21648v2, revised 29 January 2026.",
      "A. Steiger et al. (2026). Status of BICEP Array and Integration of the 220/270 GHz Receiver. Preprint arXiv:2608.25015v2, revised 27 August 2026. A status report with preliminary maps, not a new limit."
    ],
    "would_change": "An independently supported foreground separation that establishes a primordial component of the original claimed size, and explains its disagreement with the later multifrequency constraints, would change this verdict. A future detection of a much smaller r would advance the search for primordial gravitational waves without retrospectively establishing the 2014 attribution near r = 0.2.",
    "status_boundary": "A BICEP Array status paper, arXiv:2608.25015v2 (Steiger et al., revised 27 August 2026), read on 2026-09-22, says “The latest published result from the BICEP program consists of all BICEP data from 2010 through 2018 as well as external data from WMAP and Planck (BK18)” and that “a complete BK24 manuscript is currently in preparation.” The DPF 2026 conference abstract (Singari, 21 July 2026) was read for the specification; this build could not reopen it (HTTP 403 behind a browser challenge)."
  },
  "decided_by": "contamination",
  "years_to_decision": 1,
  "years_to_decision_definition": "Difference of publication years (2014 to 2015). 322 days from arXiv:1403.3985v1 (17 March 2014) to arXiv:1502.00612v1 (2 February 2015).",
  "choices": [
    {
      "id": "historical-record",
      "label": "Historical record shown",
      "options": [
        "2014 released likelihood",
        "2015 joint likelihood rerun"
      ],
      "default": "2014 released likelihood",
      "affects": [
        "displayed likelihood",
        "peak",
        "interval"
      ],
      "inert": false
    },
    {
      "id": "planted-r",
      "label": "Planted tensor amplitude",
      "options": [
        0,
        0.2
      ],
      "default": 0,
      "affects": [
        "joint bandpowers",
        "r peak",
        "profile statistic"
      ],
      "inert": false
    },
    {
      "id": "dust-prior",
      "label": "Centre of the beta_d prior (width 0.11)",
      "options": [
        1.3,
        1.59,
        1.9
      ],
      "default": 1.59,
      "affects": [
        "r curve",
        "r peak",
        "95% endpoint",
        "planted response"
      ],
      "inert": false
    },
    {
      "id": "frequency-set",
      "label": "Maps in the fit",
      "options": [
        "BK150+217+353",
        "BK150+353"
      ],
      "default": "BK150+217+353",
      "affects": [
        "selected covariance",
        "r curve",
        "95% endpoint"
      ],
      "inert": false
    }
  ],
  "explore": "A hand-fit panel scores any (r, A_d, beta_d) with the same likelihood; it is exploration of the likelihood surface, not an interpretive choice.",
  "headline": "Recomputed here, the 2014 likelihood peaks at r = 0.196 with r = 0 disfavoured at 6.96σ; the 2015 joint likelihood peaks at r = 0.048 with a 95% upper endpoint of 0.121; and r = 0.2 added to the 2015 data raises its peak by 0.200, with a profile statistic of 5.05, so this control could have confirmed the claim on this observed sky.",
  "novelty": "we searched NASA LAMBDA, GitHub and Observable on 2026-09-22 and did not find a reader-facing page that combines the original BICEP2 likelihood with a live joint HL control and a coherent r = 0.2 injection while exposing dust-prior sensitivity.",
  "second_layer": {
    "what": "Paired sensitivity: the unchanged likelihood on the measured sky and on the same sky with r = 0.2 added, at beta_d prior centres 1.3, 1.59, 1.9 and with and without the 217 GHz map",
    "result": "6 of 6 paired settings meet the declared recovery rule. Without the plant, the 95% upper endpoint ranges from 0.103 to 0.143; with r = 0.2 added, the fitted peak rises by 0.184 to 0.208 and the profile statistic reaches 3.51 to 6.47. The closest call is BK150 + 353 GHz with the prior centred on 1.30: its rise of 0.184 is 0.004 inside the rule's edge.",
    "printed_comparison": "Section III.3 prints peaks 0.021 (1.3) and 0.073 (1.9); rerun 0.020 and 0.072"
  },
  "ledger": {
    "claim_reproduced": {
      "value": true,
      "assertion": "anchor:released-2014-likelihood-rounds-to-printed"
    },
    "control_computed": {
      "value": true,
      "assertion": "control:joint-hl-within-production-tolerances"
    },
    "control_can_confirm": {
      "value": true,
      "assertion": "power:planted-r0.2-recovered-by-same-runJoint"
    },
    "rendered_figures_asserted": {
      "value": true,
      "assertion": "surface:every-data-fig-and-every-literal"
    },
    "choices_are_live": {
      "value": true,
      "assertion": "choices:record-plant-prior-maps-each-move-an-output"
    },
    "planted_fault_caught": {
      "value": true,
      "assertion": "fault:bk353-bandpowers-perturbed"
    },
    "refusal_asserted": {
      "value": true,
      "assertion": "refuse:incoherent-injection-and-out-of-domain"
    },
    "provenance_pinned": {
      "value": true,
      "assertion": "provenance:sha256-matches"
    },
    "verdict_dated": {
      "value": true,
      "assertion": "verdict:category-date-sources-evidence-printed"
    }
  }
}