Taz,
The earth's magnetic pull has little to do with it. Carbon, wood and aluminum are little affected by magnetic forces. Just try and see if a magnet will attract any one of those materials. The weights added by broadheads and field points are negligible.
The moon has it's hands full with the ocean tides, fishing schedules, the ruts, green cheese and other such phenomena.
I figure that we all wobble about as much as what the earth does so that offsets that force.
Cosmic wind....hmmmmm....now I hadn't thought of that. Normally it wouldn't amount to a hill of beans but, with the depletion of the ozone layer your might just have something there.
I'd have to have rates of depletion, speeds of cosmic winds etc., etc. Even so and "everything else being equal" <font size=2>(the disclaimer that I forgot to add to my first reply hence this reply and an end to all other unreasonable arguments)</font id=size2>, the cosmic wind would only change the flight, yes, I did say flight VC, by perhaps picometers, More realistically even as small as fentometers. Hardly a concern for splitting hairs.
Now I know why I missed that buck this past season.<img src=icon_smile_cool.gif border=0 align=middle>