Sound horizon
= Sound horizon
{title2=$r_s$}
{wiki}
The comoving sound horizon is the distance traveled by an acoustic wave,
$$
r_s(\eta)=\int_0^\eta c_s(\eta')\,d\eta'.
$$
= Sound horizon
{title2=$r_s$}
{wiki}
The comoving sound horizon is the distance traveled by an acoustic wave,
$$
r_s(\eta)=\int_0^\eta c_s(\eta')\,d\eta'.
$$