Geodesic
The path of shortest (or extreme) spacetime interval between two points in curved spacetime, representing the free-fall trajectory of particles under gravity.
Governing formula
(d²x^μ / dτ²) + Γ^μ_αβ (dx^α / dτ) (dx^β / dτ) = 0
SI unit
Spacetime Path Trajectory
In depth
In general relativity, gravity is not a force; freely falling test masses and light rays follow curved geodesics through curved spacetime determined by Christoffel symbols Γ^μ_αβ.
Examples in the real world
Planetary orbits around the Sun following timelike geodesics through curved Solar System spacetime.