the outside frame of reference is the entire universe itself. astrophysis know that we are moving, but that its rather hard to determine the speed with which we are, because of the lack of reference. We know this because we know that we are not at the center of the galaxy and everthing is moving, that means we are moving as well. One day they will likely be able to determine not only the speed at which things are moving away from us, but the angle as well. given a good understanding of the effects of gravity, and the directions things are actually moving, not just relative to us, but to everything, someone, someday will figure out the spot that the big bang (if it is still accepted as a theory and has not been supplanted but a better one) occured. Unfortunately, that is not likely to happen in even our grandchildren's grandchildrens day.
