$$
  {\rm age\ } \sim  {{\rm distance}\over{\rm speed}}  
                 = {{\rm Mpc}\over{\rm km/s}}
$$

$$
  {\rm age\ } \sim  {{\rm Mpc}\over{\rm km/s}}  
                   = { \bigl({{\rm km/s}\over{\rm Mpc}}\bigr) }^{-1}
                   = { \bigl(H_0 \bigr)^{-1} }
$$


$$
  \Omega \leq \Omega_0,  {\rm \qquad  \ universe\ expands\ forever }
$$

$$
  \Omega > \Omega_0,  {\rm \qquad  \ expansion\ halts }
$$

\bye
