# CODATA physical-constant precision control

This panel tracks the precision of a fixed set of measured physical constants across seven CODATA adjustments.

## Outcome

For each adjustment, the panel calculates the relative standard uncertainty of:

- inverse fine-structure constant;
- proton–electron mass ratio;
- muon–electron mass ratio;
- deuteron–proton mass ratio;
- neutron–proton mass ratio;
- Rydberg constant;
- electron g factor.

The primary value is their geometric mean, reported in parts per billion. The median and every individual constant remain companion views.

Lower values mean greater measurement precision.

## Editions

The fixed series contains the 1998, 2002, 2006, 2010, 2014, 2018, and 2022 CODATA adjustments.

The geometric mean relative uncertainty falls from **0.365348 ppb** in 1998 to **0.029536 ppb** in 2022, a **12.37-fold** precision improvement.

## Exclusions

Planck's constant, elementary charge, Boltzmann's constant, and Avogadro's constant are excluded. Their exact post-2019 SI values would create zero uncertainty through definition rather than measurement.

## Role

This is a **control** in fundamental physics. It is monitored, but it is not a discovery-outcome series and is not eligible for the future cross-domain discovery synthesis.

No AI exposure is assigned.

## Files

- `raw/allascii_<year>.txt` — committed NIST complete-listing ASCII tables;
- `records.csv` — one row per adjustment and constant;
- `observations.json` — aggregate values by adjustment;
- `summary.json` — edition summaries and constant trajectories;
- `source-manifest.json` — source URLs, sizes, and hashes;
- `fetch.py` — online refresh, offline rebuild, and current-table freshness check;
- `apply.py` — central registry and observation integration;
- `check.py` — consistency checks.

## Source

The source is the NIST reference on constants, units, and uncertainty. Historical editions use NIST archive tables; the 2022 edition uses NIST's current complete listing. Source attribution is retained in every record and snapshot.