metrology 0.2.5

The physical constants the physica crates share: CODATA 2018 fundamental constants, standard gravity, and the astronomical units of mass, distance and time.
Documentation

metrology

The physical constants the physica crates share, defined once: the exact SI defining constants, the CODATA 2018 values of G, α, μ₀, ε₀ and the particle masses, the flux quanta, standard gravity, and the astronomical units of mass, distance and time; plus the one-line laws of radioactive decay.

Install

cargo add metrology

Example

use metrology::{C, G, HBAR, SOLAR_MASS};

// The Schwarzschild radius of the Sun, 2GM/c²: about 2.95 km.
let r = 2.0 * G * SOLAR_MASS / (C * C);
assert!((r / 2953.3 - 1.0).abs() < 1e-3);

// The Planck length, √(ħG/c³).
assert!(((HBAR * G / C.powi(3)).sqrt() / metrology::PLANCK_LENGTH - 1.0).abs() < 1e-5);

What is inside

Group Constants Source
SI defining constants (exact) C, H, HBAR, E_CHARGE, K_B, N_A, R_GAS SI Brochure 2019
Measured G, ALPHA, MU_0, EPS_0, M_E, M_P, AMU, M_H, MU_B, MU_N, GAMMA_P, PLANCK_LENGTH CODATA 2018
Flux quanta (exact) FLUX_QUANTUM (h/2e), JOSEPHSON_CONSTANT (2e/h), DIRAC_FLUX (h/e, one Dirac monopole) SI Brochure 2019; PDG monopole review
Energy EV, KEV
Molecular binding WATER_DIMER_D0 (one hydrogen bond, 13.22 kJ/mol) Rocher-Casterline et al. 2011
decay activity, activity_step_after_suppression, ec_half_life_shift, CURIE the decay law; Pommé et al. 2016 and Ohtsuki et al. 2004 for the tests
Derived couplings EINSTEIN_KAPPA (8πG/c⁴) Einstein field equations
Earth and astronomy G0, GM_EARTH, EARTH_ROTATION, MOON_EARTH_MASS_RATIO, GM_MOON, WGS84_A, WGS84_F, GM_SUN, SOLAR_MASS, AU, PARSEC, MPC, YEAR IERS Conventions 2010; IAU 2015 B3
Reference ellipsoids and potentials GRS80_F, GRS80_GM, W0_IAU, W0_IHRS, L_G, L_B, EARTH_ANGULAR_MOMENTUM Moritz 2000; IAU 2000 B1.9 and 2006 B3; IAG 2015 Resolution 1

Applications

Anywhere a calculation must agree with another: the crates in this family all take their constants from here, so a result computed through two of them matches to the last digit. Pin the version to pin the constants, which is what reproducing a published number needs.

How it is checked

A test checks that the derived constants agree with each other: ħ = h/2π, R = N_A k_B, μ₀ε₀c² = 1, α = e²/4πε₀ħc (ħ and R are the 2019 SI's exact h/2π and N_A k_B, not CODATA's truncated digits), the Planck length, the solar mass, both magnetons, and the flux quanta (h/e = 2Φ₀, and μ₀ times the Dirac charge 3.291×10⁻⁹ A m). The decay tests reproduce radium's 0.988 Ci per gram, ⁶⁰Co's 7.2×10⁻⁴ step after a two-day stop, and ⁷Be's 0.83% half-life shift in C₆₀.

One of eight crates in physica: physica (all of them, plus cross-domain analogies) · metrology (constants) · geopotential (the gravity field) · gravimetry (missions and GRACE) · gravitational (waves) · gravitics (frontier gravity) · magnetics (magnetism and MHD) · plasmoid (fusion plasma).