We want to find the radius of an object which will cause
   its escape velocity to be "c", the speed of light.

   If an object has the mass of the Earth, what radius
   is required?

                    2 * G * M         
         R    =    -----------   
                       c^2


                   2 * (6.67E-11 N*m^2/kg^2) * (5.98E24 kg)
              =   ------------------------------------------
                         (2.9979E8 m/s)^2


              =    0.0089 m    =  8.9 mm



   If an object has the mass of the Sun, what radius
   is required?

                    2 * G * M         
         R    =    -----------   
                       c^2


                   2 * (6.67E-11 N*m^2/kg^2) * (1.99E30 kg)
              =   ------------------------------------------
                         (2.9979E8 m/s)^2


              =    2900  m    =   2.9   km