Hi again, Thaks for previous help. I am self studying GR using Schutz and Dunsby's webpages & notes. I am stuck on a step in the derivation of the weak field approximation. They approximate the metric with g[a][/b]=n[a]+epsilon h[a] In step 7.30 the partial derivative h,is taken as zero to get (7.30), -1/2 epsilon h00,i He has neglected the time derivative! Can you explain Why?? Thanks for any help!!!