metrology 0.2.1

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, standard gravity, and the astronomical units of mass, distance and time.

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, GAMMA_P, PLANCK_LENGTH CODATA 2018
Energy EV, KEV
Derived couplings EINSTEIN_KAPPA (8πG/c⁴) Einstein field equations
Earth and astronomy G0, GM_EARTH, WGS84_A, WGS84_F, GM_SUN, SOLAR_MASS, AU, PARSEC, MPC, YEAR IERS Conventions 2010; IAU 2015 B3

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, the Planck length, and the solar mass.

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).