An Etymological Dictionary of Astronomy and Astrophysics

The characteristic time it would take a body to collapse under its own → gravitational attraction, if no other forces existed to oppose the collapse. It is given by: t_ff = (3π/32 ρ₀ G)^1/2,
where ρ₀ denotes the initial density and G the → gravitational constant. Free-fall time is independent of the starting radius. Also known as → dynamical time scale.

See also: → free fall; → time.