The physics of cannonballs, planets, and pendulums.
Light, charge, and the field that holds the world together.
The weirdness that hides at the edges of speed.
Heat, entropy, and why time moves forward.
The rules the universe actually runs on.
From the nucleus to the Standard Model and beyond.
Instruments, concepts, and phenomena — the shared vocabulary of the site.
The non-abelian generalisation of Maxwell's equations: D_μ F^{aμν} = J^{aν}, where the covariant derivative D_μ = ∂_μ + i g [A_μ, ·] couples the gauge field to itself through the structure constants of the gauge group. The field equations of every non-abelian gauge theory in physics.