How is it possible to compensate for LIGO's movement in the recent measurement of Gravitational Waves? I can understand that we are able to measure something to a tiny fraction of a proton when the subject and observer are both moving relative to each other through space but how is it possible when measuring Gravitational Waves. The waves are traveling across the universe, so the subject and observer are not moving relative to each other. LIGO is moving in so many complicated directions and at speed. We have earths rotational speed at the latitude of observation with earth's axis wobble, earths rotation and trajectory about the sun, the suns rotation and trajectory about the Milky way etcetera. Surely these compounded arcs of movement, speeds and precise angles at the moment of measuring a Gravitational Wave are not known exactly and would have to be calculated from older measurements that were not take to the same level of accuracy as the LIGO experiment is working at. Can this movement really be worked out accurately enough to give an absolute reading to such a small degree? How is it done?