physics_constants
Look up the CODATA 2022 recommended values of the fundamental physical constants by symbol, exact name or keywords: value, standard uncertainty, relative uncertainty, unit, concise notation such as 9.1093837139(28)e-31 and whether the value is exact in the 2019 SI. All 355 constants of NIST's complete listing are bundled in a dated table; every answer names the source and fetch date.
Install
/tools install physics_constants /tools install physics_constants@1.0.0
In a console session, or let the model find it in normal mode: axlr_catalog describes it and axlr_install_tool asks for the same install card. The card reads catalog axlr · physics_constants 1.0.0 · verified once the index signature, the manifest digest and every file digest check out. Then the model runs it with axlr_run_tool physics_constants; each run is approved as a local_exec.
Arguments
One JSON object on stdin, validated against the schema before the program starts.
| name | type | required | default | meaning |
|---|---|---|---|---|
query | string | no | A symbol (h, m_e, N_A), an exact name, or keywords ("proton mass"). length ≤ 200 | |
name | string | no | Exact quantity name as NIST prints it, case-insensitive. length ≤ 200 | |
symbol | string | no | length ≤ 200 | |
list | boolean | no | List every constant name and its symbols | |
limit | integer | no | 10 | Maximum keyword matches returned. ≥ 1; ≤ 400 |
Input schema (JSON)
{
"type": "object",
"additionalProperties": false,
"properties": {
"query": {
"type": "string",
"maxLength": 200,
"description": "A symbol (h, m_e, N_A), an exact name, or keywords (\"proton mass\")"
},
"name": {
"type": "string",
"maxLength": 200,
"description": "Exact quantity name as NIST prints it, case-insensitive"
},
"symbol": {
"type": "string",
"maxLength": 200
},
"list": {
"type": "boolean",
"description": "List every constant name and its symbols"
},
"limit": {
"type": "integer",
"minimum": 1,
"maximum": 400,
"default": 10,
"description": "Maximum keyword matches returned"
}
}
}Example
Input
{
"query": "electron mass"
}Output (stdout)
{
"match": "name",
"results": [
{
"name": "electron mass",
"value": "9.1093837139e-31",
"uncertainty": "2.8e-40",
"unit": "kg",
"exact": false,
"concise": "9.1093837139(28)e-31"
}
]
}Files
The command the install card registers is python3 physics_constants.py, run in the workspace with PATH and HOME as its only environment. Each file's SHA-256 is in the signed index; the console checks them before showing the card and again before writing.
constants.json · sha256 6832bcbc4e830a0c21dad64e0d67f0e15e3c28121f130f4b69d4f837a3f84249
{
"title": "CODATA 2022 recommended values of the fundamental physical constants",
"source": "NIST Fundamental Physical Constants, Complete Listing, 2022 CODATA adjustment",
"source_url": "https://physics.nist.gov/cuu/Constants/Table/allascii.txt",
"licence": "public domain (U.S. Government work, 17 U.S.C. 105)",
"fetched": "2026-10-18",
"generator": "tools/catalog/data/physics_constants.py",
"symbols_note": "symbols are the generator's own list of the usual symbols, not part of the NIST file",
"constants": [
{
"name": "alpha particle-electron mass ratio",
"value": "7294.29954171",
"uncertainty": "0.00000017",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle mass",
"value": "6.6446573450e-27",
"uncertainty": "0.0000000021e-27",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle mass energy equivalent",
"value": "5.9719201997e-10",
"uncertainty": "0.0000000019e-10",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle mass energy equivalent in MeV",
"value": "3727.3794118",
"uncertainty": "0.0000012",
"unit": "MeV",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle mass in u",
"value": "4.001506179129",
"uncertainty": "0.000000000062",
"unit": "u",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle molar mass",
"value": "4.0015061833e-3",
"uncertainty": "0.0000000012e-3",
"unit": "kg mol^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle-proton mass ratio",
"value": "3.972599690252",
"uncertainty": "0.000000000070",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle relative atomic mass",
"value": "4.001506179129",
"uncertainty": "0.000000000062",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "alpha particle rms charge radius",
"value": "1.6785e-15",
"uncertainty": "0.0021e-15",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Angstrom star",
"value": "1.00001495e-10",
"uncertainty": "0.00000090e-10",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass constant",
"value": "1.66053906892e-27",
"uncertainty": "0.00000000052e-27",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": [
"m_u",
"mu",
"u"
]
},
{
"name": "atomic mass constant energy equivalent",
"value": "1.49241808768e-10",
"uncertainty": "0.00000000046e-10",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass constant energy equivalent in MeV",
"value": "931.49410372",
"uncertainty": "0.00000029",
"unit": "MeV",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass unit-electron volt relationship",
"value": "9.3149410372e8",
"uncertainty": "0.0000000029e8",
"unit": "eV",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass unit-hartree relationship",
"value": "3.4231776922e7",
"uncertainty": "0.0000000011e7",
"unit": "E_h",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass unit-hertz relationship",
"value": "2.25234272185e23",
"uncertainty": "0.00000000070e23",
"unit": "Hz",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass unit-inverse meter relationship",
"value": "7.5130066209e14",
"uncertainty": "0.0000000023e14",
"unit": "m^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass unit-joule relationship",
"value": "1.49241808768e-10",
"uncertainty": "0.00000000046e-10",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass unit-kelvin relationship",
"value": "1.08095402067e13",
"uncertainty": "0.00000000034e13",
"unit": "K",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic mass unit-kilogram relationship",
"value": "1.66053906892e-27",
"uncertainty": "0.00000000052e-27",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of 1st hyperpolarizability",
"value": "3.2063612996e-53",
"uncertainty": "0.0000000015e-53",
"unit": "C^3 m^3 J^-2",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of 2nd hyperpolarizability",
"value": "6.2353799735e-65",
"uncertainty": "0.0000000039e-65",
"unit": "C^4 m^4 J^-3",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of action",
"value": "1.054571817e-34",
"uncertainty": null,
"unit": "J s",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "atomic unit of charge",
"value": "1.602176634e-19",
"uncertainty": null,
"unit": "C",
"exact": true,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of charge density",
"value": "1.08120238677e12",
"uncertainty": "0.00000000051e12",
"unit": "C m^-3",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of current",
"value": "6.6236182375082e-3",
"uncertainty": "0.0000000000072e-3",
"unit": "A",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of electric dipole mom.",
"value": "8.4783536198e-30",
"uncertainty": "0.0000000013e-30",
"unit": "C m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of electric field",
"value": "5.14220675112e11",
"uncertainty": "0.00000000080e11",
"unit": "V m^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of electric field gradient",
"value": "9.7173624424e21",
"uncertainty": "0.0000000030e21",
"unit": "V m^-2",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of electric polarizability",
"value": "1.64877727212e-41",
"uncertainty": "0.00000000051e-41",
"unit": "C^2 m^2 J^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of electric potential",
"value": "27.211386245981",
"uncertainty": "0.000000000030",
"unit": "V",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of electric quadrupole mom.",
"value": "4.4865515185e-40",
"uncertainty": "0.0000000014e-40",
"unit": "C m^2",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of energy",
"value": "4.3597447222060e-18",
"uncertainty": "0.0000000000048e-18",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of force",
"value": "8.2387235038e-8",
"uncertainty": "0.0000000013e-8",
"unit": "N",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of length",
"value": "5.29177210544e-11",
"uncertainty": "0.00000000082e-11",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of mag. dipole mom.",
"value": "1.85480201315e-23",
"uncertainty": "0.00000000058e-23",
"unit": "J T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of mag. flux density",
"value": "2.35051757077e5",
"uncertainty": "0.00000000073e5",
"unit": "T",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of magnetizability",
"value": "7.8910365794e-29",
"uncertainty": "0.0000000049e-29",
"unit": "J T^-2",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of mass",
"value": "9.1093837139e-31",
"uncertainty": "0.0000000028e-31",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of momentum",
"value": "1.99285191545e-24",
"uncertainty": "0.00000000031e-24",
"unit": "kg m s^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of permittivity",
"value": "1.11265005620e-10",
"uncertainty": "0.00000000017e-10",
"unit": "F m^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of time",
"value": "2.4188843265864e-17",
"uncertainty": "0.0000000000026e-17",
"unit": "s",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "atomic unit of velocity",
"value": "2.18769126216e6",
"uncertainty": "0.00000000034e6",
"unit": "m s^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Avogadro constant",
"value": "6.02214076e23",
"uncertainty": null,
"unit": "mol^-1",
"exact": true,
"truncated": false,
"symbols": [
"N_A",
"NA",
"L"
]
},
{
"name": "Bohr magneton",
"value": "9.2740100657e-24",
"uncertainty": "0.0000000029e-24",
"unit": "J T^-1",
"exact": false,
"truncated": false,
"symbols": [
"mu_B",
"muB",
"μB"
]
},
{
"name": "Bohr magneton in eV/T",
"value": "5.7883817982e-5",
"uncertainty": "0.0000000018e-5",
"unit": "eV T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Bohr magneton in Hz/T",
"value": "1.39962449171e10",
"uncertainty": "0.00000000044e10",
"unit": "Hz T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Bohr magneton in inverse meter per tesla",
"value": "46.686447719",
"uncertainty": "0.000000015",
"unit": "m^-1 T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Bohr magneton in K/T",
"value": "0.67171381472",
"uncertainty": "0.00000000021",
"unit": "K T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Bohr radius",
"value": "5.29177210544e-11",
"uncertainty": "0.00000000082e-11",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": [
"a_0",
"a0"
]
},
{
"name": "Boltzmann constant",
"value": "1.380649e-23",
"uncertainty": null,
"unit": "J K^-1",
"exact": true,
"truncated": false,
"symbols": [
"k",
"k_B",
"kB"
]
},
{
"name": "Boltzmann constant in eV/K",
"value": "8.617333262e-5",
"uncertainty": null,
"unit": "eV K^-1",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "Boltzmann constant in Hz/K",
"value": "2.083661912e10",
"uncertainty": null,
"unit": "Hz K^-1",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "Boltzmann constant in inverse meter per kelvin",
"value": "69.50348004",
"uncertainty": null,
"unit": "m^-1 K^-1",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "characteristic impedance of vacuum",
"value": "376.730313412",
"uncertainty": "0.000000059",
"unit": "ohm",
"exact": false,
"truncated": false,
"symbols": [
"Z_0",
"Z0"
]
},
{
"name": "classical electron radius",
"value": "2.8179403205e-15",
"uncertainty": "0.0000000013e-15",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": [
"r_e",
"re"
]
},
{
"name": "Compton wavelength",
"value": "2.42631023538e-12",
"uncertainty": "0.00000000076e-12",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": [
"lambda_C",
"λC"
]
},
{
"name": "conductance quantum",
"value": "7.748091729e-5",
"uncertainty": null,
"unit": "S",
"exact": true,
"truncated": true,
"symbols": [
"G_0",
"G0"
]
},
{
"name": "conventional value of ampere-90",
"value": "1.00000008887",
"uncertainty": null,
"unit": "A",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "conventional value of coulomb-90",
"value": "1.00000008887",
"uncertainty": null,
"unit": "C",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "conventional value of farad-90",
"value": "0.99999998220",
"uncertainty": null,
"unit": "F",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "conventional value of henry-90",
"value": "1.00000001779",
"uncertainty": null,
"unit": "H",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "conventional value of Josephson constant",
"value": "483597.9e9",
"uncertainty": null,
"unit": "Hz V^-1",
"exact": true,
"truncated": false,
"symbols": []
},
{
"name": "conventional value of ohm-90",
"value": "1.00000001779",
"uncertainty": null,
"unit": "ohm",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "conventional value of volt-90",
"value": "1.00000010666",
"uncertainty": null,
"unit": "V",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "conventional value of von Klitzing constant",
"value": "25812.807",
"uncertainty": null,
"unit": "ohm",
"exact": true,
"truncated": false,
"symbols": []
},
{
"name": "conventional value of watt-90",
"value": "1.00000019553",
"uncertainty": null,
"unit": "W",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "Copper x unit",
"value": "1.00207697e-13",
"uncertainty": "0.00000028e-13",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron-electron mag. mom. ratio",
"value": "-4.664345550e-4",
"uncertainty": "0.000000012e-4",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron-electron mass ratio",
"value": "3670.482967655",
"uncertainty": "0.000000063",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron g factor",
"value": "0.8574382335",
"uncertainty": "0.0000000022",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron mag. mom.",
"value": "4.330735087e-27",
"uncertainty": "0.000000011e-27",
"unit": "J T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron mag. mom. to Bohr magneton ratio",
"value": "4.669754568e-4",
"uncertainty": "0.000000012e-4",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron mag. mom. to nuclear magneton ratio",
"value": "0.8574382335",
"uncertainty": "0.0000000022",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron mass",
"value": "3.3435837768e-27",
"uncertainty": "0.0000000010e-27",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron mass energy equivalent",
"value": "3.00506323491e-10",
"uncertainty": "0.00000000094e-10",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron mass energy equivalent in MeV",
"value": "1875.61294500",
"uncertainty": "0.00000058",
"unit": "MeV",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron mass in u",
"value": "2.013553212544",
"uncertainty": "0.000000000015",
"unit": "u",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron molar mass",
"value": "2.01355321466e-3",
"uncertainty": "0.00000000063e-3",
"unit": "kg mol^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron-neutron mag. mom. ratio",
"value": "-0.44820652",
"uncertainty": "0.00000011",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron-proton mag. mom. ratio",
"value": "0.30701220930",
"uncertainty": "0.00000000079",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron-proton mass ratio",
"value": "1.9990075012699",
"uncertainty": "0.0000000000084",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron relative atomic mass",
"value": "2.013553212544",
"uncertainty": "0.000000000015",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "deuteron rms charge radius",
"value": "2.12778e-15",
"uncertainty": "0.00027e-15",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "electron charge to mass quotient",
"value": "-1.75882000838e11",
"uncertainty": "0.00000000055e11",
"unit": "C kg^-1",
"exact": false,
"truncated": false,
"symbols": [
"-e/m_e"
]
},
{
"name": "electron-deuteron mag. mom. ratio",
"value": "-2143.9234921",
"uncertainty": "0.0000056",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "electron-deuteron mass ratio",
"value": "2.724437107629e-4",
"uncertainty": "0.000000000047e-4",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "electron g factor",
"value": "-2.00231930436092",
"uncertainty": "0.00000000000036",
"unit": "",
"exact": false,
"truncated": false,
"symbols": [
"g_e",
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{
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{
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{
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{
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{
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{
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{
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{
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{
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{
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{
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{
"name": "reduced Planck constant",
"value": "1.054571817e-34",
"uncertainty": null,
"unit": "J s",
"exact": true,
"truncated": true,
"symbols": [
"hbar",
"ħ"
]
},
{
"name": "reduced Planck constant in eV s",
"value": "6.582119569e-16",
"uncertainty": null,
"unit": "eV s",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "reduced Planck constant times c in MeV fm",
"value": "197.3269804",
"uncertainty": null,
"unit": "MeV fm",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "reduced proton Compton wavelength",
"value": "2.10308910051e-16",
"uncertainty": "0.00000000066e-16",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "reduced tau Compton wavelength",
"value": "1.110538e-16",
"uncertainty": "0.000075e-16",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Rydberg constant",
"value": "10973731.568157",
"uncertainty": "0.000012",
"unit": "m^-1",
"exact": false,
"truncated": false,
"symbols": [
"R_inf",
"Rinf",
"R∞"
]
},
{
"name": "Rydberg constant times c in Hz",
"value": "3.2898419602500e15",
"uncertainty": "0.0000000000036e15",
"unit": "Hz",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Rydberg constant times hc in eV",
"value": "13.605693122990",
"uncertainty": "0.000000000015",
"unit": "eV",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Rydberg constant times hc in J",
"value": "2.1798723611030e-18",
"uncertainty": "0.0000000000024e-18",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Sackur-Tetrode constant (1 K, 100 kPa)",
"value": "-1.15170753496",
"uncertainty": "0.00000000047",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Sackur-Tetrode constant (1 K, 101.325 kPa)",
"value": "-1.16487052149",
"uncertainty": "0.00000000047",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "second radiation constant",
"value": "1.438776877e-2",
"uncertainty": null,
"unit": "m K",
"exact": true,
"truncated": true,
"symbols": [
"c_2",
"c2"
]
},
{
"name": "shielded helion gyromag. ratio",
"value": "2.0378946078e8",
"uncertainty": "0.0000000018e8",
"unit": "s^-1 T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded helion gyromag. ratio in MHz/T",
"value": "32.434100033",
"uncertainty": "0.000000028",
"unit": "MHz T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded helion mag. mom.",
"value": "-1.07455311035e-26",
"uncertainty": "0.00000000093e-26",
"unit": "J T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded helion mag. mom. to Bohr magneton ratio",
"value": "-1.15867149457e-3",
"uncertainty": "0.00000000094e-3",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded helion mag. mom. to nuclear magneton ratio",
"value": "-2.1274977624",
"uncertainty": "0.0000000017",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded helion to proton mag. mom. ratio",
"value": "-0.76176657721",
"uncertainty": "0.00000000066",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded helion to shielded proton mag. mom. ratio",
"value": "-0.7617861334",
"uncertainty": "0.0000000031",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded proton gyromag. ratio",
"value": "2.675153194e8",
"uncertainty": "0.000000011e8",
"unit": "s^-1 T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded proton gyromag. ratio in MHz/T",
"value": "42.57638543",
"uncertainty": "0.00000017",
"unit": "MHz T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded proton mag. mom.",
"value": "1.4105705830e-26",
"uncertainty": "0.0000000058e-26",
"unit": "J T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded proton mag. mom. to Bohr magneton ratio",
"value": "1.5209931551e-3",
"uncertainty": "0.0000000062e-3",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielded proton mag. mom. to nuclear magneton ratio",
"value": "2.792775648",
"uncertainty": "0.000000011",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielding difference of d and p in HD",
"value": "1.98770e-8",
"uncertainty": "0.00010e-8",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "shielding difference of t and p in HT",
"value": "2.39450e-8",
"uncertainty": "0.00020e-8",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "speed of light in vacuum",
"value": "299792458",
"uncertainty": null,
"unit": "m s^-1",
"exact": true,
"truncated": false,
"symbols": [
"c",
"c0"
]
},
{
"name": "standard acceleration of gravity",
"value": "9.80665",
"uncertainty": null,
"unit": "m s^-2",
"exact": true,
"truncated": false,
"symbols": [
"g_n",
"gn"
]
},
{
"name": "standard atmosphere",
"value": "101325",
"uncertainty": null,
"unit": "Pa",
"exact": true,
"truncated": false,
"symbols": [
"atm"
]
},
{
"name": "standard-state pressure",
"value": "100000",
"uncertainty": null,
"unit": "Pa",
"exact": true,
"truncated": false,
"symbols": []
},
{
"name": "Stefan-Boltzmann constant",
"value": "5.670374419e-8",
"uncertainty": null,
"unit": "W m^-2 K^-4",
"exact": true,
"truncated": true,
"symbols": [
"sigma",
"σ"
]
},
{
"name": "tau Compton wavelength",
"value": "6.97771e-16",
"uncertainty": "0.00047e-16",
"unit": "m",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau-electron mass ratio",
"value": "3477.23",
"uncertainty": "0.23",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau energy equivalent",
"value": "1776.86",
"uncertainty": "0.12",
"unit": "MeV",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau mass",
"value": "3.16754e-27",
"uncertainty": "0.00021e-27",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau mass energy equivalent",
"value": "2.84684e-10",
"uncertainty": "0.00019e-10",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau mass in u",
"value": "1.90754",
"uncertainty": "0.00013",
"unit": "u",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau molar mass",
"value": "1.90754e-3",
"uncertainty": "0.00013e-3",
"unit": "kg mol^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau-muon mass ratio",
"value": "16.8170",
"uncertainty": "0.0011",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau-neutron mass ratio",
"value": "1.89115",
"uncertainty": "0.00013",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "tau-proton mass ratio",
"value": "1.89376",
"uncertainty": "0.00013",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Thomson cross section",
"value": "6.6524587051e-29",
"uncertainty": "0.0000000062e-29",
"unit": "m^2",
"exact": false,
"truncated": false,
"symbols": [
"sigma_e",
"σe"
]
},
{
"name": "triton-electron mass ratio",
"value": "5496.92153551",
"uncertainty": "0.00000021",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton g factor",
"value": "5.957924930",
"uncertainty": "0.000000012",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton mag. mom.",
"value": "1.5046095178e-26",
"uncertainty": "0.0000000030e-26",
"unit": "J T^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton mag. mom. to Bohr magneton ratio",
"value": "1.6223936648e-3",
"uncertainty": "0.0000000032e-3",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton mag. mom. to nuclear magneton ratio",
"value": "2.9789624650",
"uncertainty": "0.0000000059",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton mass",
"value": "5.0073567512e-27",
"uncertainty": "0.0000000016e-27",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton mass energy equivalent",
"value": "4.5003878119e-10",
"uncertainty": "0.0000000014e-10",
"unit": "J",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton mass energy equivalent in MeV",
"value": "2808.92113668",
"uncertainty": "0.00000088",
"unit": "MeV",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton mass in u",
"value": "3.01550071597",
"uncertainty": "0.00000000010",
"unit": "u",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton molar mass",
"value": "3.01550071913e-3",
"uncertainty": "0.00000000094e-3",
"unit": "kg mol^-1",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton-proton mass ratio",
"value": "2.99371703403",
"uncertainty": "0.00000000010",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton relative atomic mass",
"value": "3.01550071597",
"uncertainty": "0.00000000010",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "triton to proton mag. mom. ratio",
"value": "1.0666399189",
"uncertainty": "0.0000000021",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "unified atomic mass unit",
"value": "1.66053906892e-27",
"uncertainty": "0.00000000052e-27",
"unit": "kg",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "vacuum electric permittivity",
"value": "8.8541878188e-12",
"uncertainty": "0.0000000014e-12",
"unit": "F m^-1",
"exact": false,
"truncated": false,
"symbols": [
"epsilon_0",
"eps0",
"ε0"
]
},
{
"name": "vacuum mag. permeability",
"value": "1.25663706127e-6",
"uncertainty": "0.00000000020e-6",
"unit": "N A^-2",
"exact": false,
"truncated": false,
"symbols": [
"mu_0",
"mu0",
"μ0"
]
},
{
"name": "von Klitzing constant",
"value": "25812.80745",
"uncertainty": null,
"unit": "ohm",
"exact": true,
"truncated": true,
"symbols": [
"R_K",
"RK"
]
},
{
"name": "weak mixing angle",
"value": "0.22305",
"uncertainty": "0.00023",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
},
{
"name": "Wien frequency displacement law constant",
"value": "5.878925757e10",
"uncertainty": null,
"unit": "Hz K^-1",
"exact": true,
"truncated": true,
"symbols": []
},
{
"name": "Wien wavelength displacement law constant",
"value": "2.897771955e-3",
"uncertainty": null,
"unit": "m K",
"exact": true,
"truncated": true,
"symbols": [
"b"
]
},
{
"name": "W to Z mass ratio",
"value": "0.88145",
"uncertainty": "0.00013",
"unit": "",
"exact": false,
"truncated": false,
"symbols": []
}
]
}
physics_constants.py · sha256 92c5d237b402391b16829071274433660c1d34152b74b27e2434e3fc7f5380ce
#!/usr/bin/env python3
"""Look up the CODATA 2022 recommended values of the fundamental physical constants from the
bundled table constants.json (written from NIST's allascii.txt by
tools/catalog/data/physics_constants.py).
Input (JSON on stdin), one of:
query free text: a symbol ("h", "m_e"), an exact name, or keywords ("electron mass")
name exact quantity name as NIST prints it (case-insensitive)
symbol exact symbol from the bundled symbol list
list true: list every name (with symbols), no values
limit maximum keyword matches, default 10 (1-400)
"""
import json
import pathlib
import re
import sys
from decimal import Decimal
TABLE = pathlib.Path(__file__).resolve().parent / "constants.json"
def fail(message):
print(json.dumps({"error": message}))
sys.exit(2)
def split(text):
mantissa, _, exponent = text.partition("e")
return mantissa, exponent
def concise(value, uncertainty):
"""9.1093837139e-31 with 0.0000000028e-31 -> 9.1093837139(28)e-31, when the digits line up."""
vm, ve = split(value)
um, ue = split(uncertainty)
if ve != ue or "." not in vm or "." not in um:
return None
if len(vm.split(".")[1]) != len(um.split(".")[1]):
return None
digits = um.replace(".", "").lstrip("0")
if not digits:
return None
return f"{vm}({digits})" + (f"e{ve}" if ve else "")
def describe(c):
out = {"name": c["name"], "symbols": c["symbols"], "value": c["value"], "value_float": float(c["value"]),
"unit": c["unit"], "exact": c["exact"]}
if c["exact"]:
out["uncertainty"] = None
out["relative_uncertainty"] = 0
if c["truncated"]:
out["note"] = "exact, but NIST prints it truncated (more digits follow)"
else:
u = Decimal(c["uncertainty"])
out["uncertainty"] = format(u.normalize(), "e")
out["uncertainty_float"] = float(u)
out["relative_uncertainty"] = float(f"{float(u / abs(Decimal(c['value']))):.2e}")
out["concise"] = concise(c["value"], c["uncertainty"])
return out
def tokens(text):
return [t for t in re.split(r"[^a-z0-9]+", text.lower()) if t]
def main():
try:
request = json.load(sys.stdin)
except ValueError as error:
fail(f"stdin is not JSON: {error}")
if not isinstance(request, dict):
fail("input must be a JSON object")
allowed = {"query", "name", "symbol", "list", "limit"}
extra = set(request) - allowed
if extra:
fail(f"unknown field(s): {', '.join(sorted(extra))}")
try:
table = json.loads(TABLE.read_text(encoding="utf-8"))
except (OSError, ValueError) as error:
fail(f"cannot read the bundled table: {error}")
constants = table["constants"]
source = {"title": table["title"], "source": table["source"], "url": table["source_url"],
"licence": table["licence"], "fetched": table["fetched"]}
limit = request.get("limit", 10)
if isinstance(limit, bool) or not isinstance(limit, int) or not 1 <= limit <= 400:
fail("limit must be an integer from 1 to 400")
given = [k for k in ("query", "name", "symbol", "list") if k in request]
if len(given) != 1:
fail("give exactly one of query, name, symbol or list")
key = given[0]
if key == "list":
if request["list"] is not True:
fail("list must be true")
print(json.dumps({"count": len(constants), "constants": [{"name": c["name"], "symbols": c["symbols"]} for c in constants],
"source": source}, ensure_ascii=False))
return
text = request[key]
if not isinstance(text, str) or not text.strip() or len(text) > 200:
fail(f"{key} must be a non-empty string of at most 200 characters")
text = text.strip()
by_symbol = [c for c in constants if text in c["symbols"]] or \
[c for c in constants if text.lower() in (s.lower() for s in c["symbols"])]
by_name = [c for c in constants if c["name"].lower() == text.lower()]
if key == "symbol":
found, how = by_symbol, "symbol"
elif key == "name":
found, how = by_name, "name"
elif by_name:
found, how = by_name, "name"
elif by_symbol:
found, how = by_symbol, "symbol"
else:
words = tokens(text)
if not words:
fail("query has no letters or digits")
hits = []
for c in constants:
name_words = tokens(c["name"])
if all(any(n.startswith(w) for n in name_words) for w in words):
starts = c["name"].lower().startswith(text.lower())
hits.append((0 if starts else 1, len(c["name"]), c["name"], c))
hits.sort(key=lambda h: h[:3])
found, how = [h[3] for h in hits], "keywords"
if not found:
print(json.dumps({"query": text, "match": how, "count": 0, "results": [], "source": source,
"hint": "try fewer keywords, or list: true for every name"}, ensure_ascii=False))
return
total = len(found)
print(json.dumps({"query": text, "match": how, "count": total, "results": [describe(c) for c in found[:limit]],
"truncated": total > limit, "source": source}, ensure_ascii=False))
if __name__ == "__main__":
try:
main()
except SystemExit:
raise
except Exception as error: # never a traceback
fail(f"{type(error).__name__}: {error}")
Where it is served
The registry serves only AXLR clients, so a browser gets 403; fetch with a User-Agent that starts with axlr:
curl -A axlr-docs/1.0 -O https://registry.underpassai.com/tools/physics_constants/1.0.0/manifest.json
curl -A axlr-docs/1.0 -O https://registry.underpassai.com/tools/physics_constants/1.0.0/constants.json
curl -A axlr-docs/1.0 -O https://registry.underpassai.com/tools/physics_constants/1.0.0/physics_constants.py