Q:  What are the units of distance?

             Parsecs -- but since the numbers are so large,
             it makes sense to use millions of parsecs = Megaparsecs

             The abbreviation for Megaparsecs is "Mpc"


  Q:  What are the units of radial velocity?

             Although the label on this figure says "kilometers,"
             the valocities are actually measured in "kilometers per second."

             The abbreviation for "kilometers per second" is "km/sec"


  Q:  What is the slope -- both size and units?

             The units must be 

                              rise         km/sec
                  slope  =  --------  =  -----------
                              run           Mpc


             The value of the slope in this diagram is about


                   H0  =   500 km/sec/Mpc