I have prepared this photo for you in the hope that it may answer your question.
I chose a swing video of Tiger Woods where the camera was positioned at an angle, that would be more-or-less in line with the direction the hands would follow on their path to their impact location. I then used a spline tool to trace the hand arc path.
You can see that the hand arc path is U-shaped. It is impossible for the left hand to travel in a straight line in a full golf swing - because the left hand is merely the end of the left arm lever, which is swinging from a fulcrum point (left shoulder socket joint). Theoretically, the left hand should swing in a circular arc - if the left shoulder remained stationary in space. However, during the downswing, the left shoulder socket (fulcrum point for the left arm lever) is moving down-out-forward and that changes a circular hand arc path into an U-shaped handarc path.
However, as Yoda stated, it "feels" like one is pulling the hands down in a straight line thrust direction towards an aiming point.
Jeff.
Jeff,
I really like that explanation. Before I started studying TGM, I believed the hands moved in a circle. In the book, Diane's hands are always moving in the same way as your picture of Tiger. Probably very basic stuff to you guys, but as a rookie I appreciate the help you just gave in understanding why...
Thanks,
Kevin
__________________
I could be wrong. I have been before, and will be again.