We make a sail of aluminum foil, 1 meter by 1 meter on a side.

  The thickness of foil is 16 micrometers, and the density of aluminum
        is 2700 kg / cubic meter.

  Q:  What is the mass of this sail?


            m  =  2700 kg/m^3  *  (16 x 10^(-6)) m  *  (1 m^2)

               =  0.43 kg

               =  43 g


  Q:  If the Sun emits as a blackbody at T = 5800 K, what is the
        what is the radiation pressure on the sail?
        This is equivalent to the force on the sail, pushing
        away from the Sun.

            P  =  (1/3) * 7.566 x 10^(-16) * (5800)^4 

            P  =  0.28  N/m^2  

        so

            Force of radiation  =  0.28  N    away from Sun