Apparently what I thought I understood about waves is wrong: there seems to be a net momentum transfer with mechanical waves, as well as photons (it seems they're perfectly analogous). I hope some of the experts on the board can help to clarify this issue; perhaps it’s less surprising to others here than it is to me. I recently found this discussion on the topic of wave momentum started by Carl Mungan, Associate Professor at the US Naval Academy: http://www.usna.edu/Users/physics/mungan/Scholarship/WaveMomentum.html There’s a list of references at the bottom of the page, and this reference was cited in Dr. Mungan’s last post as his key reference: Reuben Benumof, "Simple harmonic motion in harmonic waves," AJP 48, 387-392 (May 1980) If this is true, then everything else I’ve read online about wave momentum, and all the applets I’ve seen, are wrong (or at least confined to one special case scenario). And following the discussion in that link, it appears that most physics professors also incorrectly believe that mechanical waves transfer zero net momentum. This question has gotten me thinking that maybe we can interpret any wave in the manner QM describes photons, as both a wave and a particle. Help?