Why Does A Wave Move As It Does!? My friend, being a highly religious and faith filled person, has come up with several question for me to answer without having to revert to the idea that divine intervention of some sort is involved. On of them is...why does a wave move like it does? What influences a wave to follow the up and down motion, as opposed to moving in a straight line. I must say i couldn't answer the question. And being a pesimist when it comes to religious matters, i know there must be a logical explanation. So...anyone? Thanks!!