Q:  The galaxy M87 has a radial velocity of v = 1280 km/s
             away from the solar system.


         Estimate the time it takes for light to travel from M87 to Earth.


            Let's use H0 = 70 km/s/Mpc.  Then the distance to M87 is

                        1280 km/s
                d  =   --------------  =  18.3 Mpc
                         70 km/s/Mpc

                                     3.08 x 10^(22) m
                   =    18.3 Mpc *  ------------------
                                        1 Mpc


                   =    5.64 x 10^(23)  m


            So the time for light to travel from M87 to us is


                        5.64 x 10^(23) m
                t  =    -----------------   =   1.88 x 10^(15) s
                          3 x 10^(8) m/s


                   =    6.0 x 10^(7) years  =   60 Myr