Physics Data
A comprehensive repository of physical data across all domains of physics — every value accompanied by its uncertainty, so you always know the frontier of what remains to be measured.
Values that are defined exactly (e.g., the speed of light, c = 299 792 458 m/s) are marked as having no uncertainty. For everything else, the stated uncertainty tells you both how well we know the value and where precision measurement can still advance the field.
Particle Physics
AvailableMasses, lifetimes, charges, and decay modes of all known fundamental and composite particles.
- Lepton & quark masses
- Gauge boson masses (W, Z, Higgs)
- Fundamental coupling constants (α, α_s, G_F)
- Particle lifetimes & decay modes
- Magnetic moments & charges
- CKM & PMNS matrix elements
Atomic & Nuclear
AvailableAtomic masses, ionization energies, spectral line wavelengths, nuclear spins, and magnetic moments for every element.
- Atomic masses & isotope abundances
- Ionization energies (1st, 2nd, …)
- Electron affinities & radii
- Spectral emission lines
- Nuclear spins, moments & binding energies
- Radioactive half-lives
Molecular
AvailableBond lengths and angles, dissociation energies, vibrational frequencies, dipole moments, and polarizabilities for common molecules.
- Bond lengths & bond angles
- Bond dissociation energies
- Vibrational & rotational constants
- Electric dipole moments
- Molecular polarizabilities
- Enthalpies of formation & reaction
Metallic & Material
AvailableTransport and thermodynamic properties of metals and materials — resistivity, Fermi energy, work function, and superconducting critical temperatures.
- Electrical resistivity (with temp. dependence)
- Thermal conductivity
- Fermi energy & electron density
- Work functions
- Superconducting critical temperatures T_c
- Density, melting & boiling points
Astronomical
AvailablePlanetary, stellar, galactic, and cosmological data — from the mass of the Sun to the Hubble constant — all with their current best-known uncertainties.
- Planetary masses, radii & orbital elements
- Solar & stellar properties
- Galactic structure parameters
- Cosmological parameters (H₀, Ω_m, Ω_Λ)
- CMB temperature & anisotropy spectrum
- Gravitational wave event parameters
Why uncertainties matter
A measured value without an uncertainty is incomplete. Uncertainty quantifies the boundary of current knowledge — the Hubble constant (H₀ ≈ 70 km/s/Mpc, ±2%) still carries a Hubble tension between early- and late-universe measurements. The more precisely we know a constant, the more sharply we can test underlying theory and design new experiments. Every data point here includes its best-known uncertainty alongside the value and its source.