Suppose a star in Andromeda, at a distance of d = 760 kpc,
           moves with a tangential speed of v = 100 km/s relative
           to distant sources.


        Q:  How far will it move (in meters) over a span of 100 years?


                Let "w" = distance travelled tangentially.


                   w  =  100 km/s * 100 years


                      =  (10^5 m/s) * (100 * 3.15 x 10^7 s)


                      =  3.15 x 10^(14) m


        Q:  How much will its angular position change over this time?
                Express your result in arcseconds.


                distance d =  760 kpc  =  2.34 x 10^(22) m

                                    w
                angle  theta  =   -----  radians  =   1.35 x 10^(-8) radians
                                    d


                                                                arcsec
                       theta  =  1.35 x 10^(-8) rad * ( 206265 --------- )
                                                                radians


                              =  0.0028  arcsec  per century