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The question is whether any such change still fits all the detailed data.","posed_since":"","precise":"Determine whether any model that reduces the sound horizon $r_d$ by $\\sim 7\\%$ (early dark energy, extra radiation $\\Delta N_{\\mathrm{eff}}$, varying electron mass, primordial magnetic fields) fits Planck, ACT DR6 and SPT-3G CMB spectra plus DESI DR2 BAO with $h \\ge 0.72$ and total $\\chi^2$ no worse than LCDM. Answer yes with an explicit model or no with a general argument.","problem_ref":"3f3c7115666469749bd0e1a64b3770eac5e4de8fdeed3c3f2608ea2caa34db57","references":"","settled_by":"Joint fits of candidate models to current CMB and BAO data, plus a model-independent bound on $r_{d} h$ from BAO and supernovae.","status_note":"2025 ACT DR6 extended-model analyses found no preference for early dark energy or extra radiation at the level needed (moderate confidence).","title":"Can pre-recombination physics raise the Hubble constant to 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