3 ms·
In fact, sound waves literally means moving matter! Transporting mass along the wave propagation is a whole different thing. It depends on the matter that is mo
by dschuetz 8y ago
In fact, sound waves literally means moving matter! Transporting mass along the wave propagation is a whole different thing. It depends on the matter that is moving/vibrating. While the propagation of kinetic energy through a medium cannot have mass, the mean mass transport through a closed surface should equal zero. However, if they've discovered that it, in fact, isn't - then it's a big deal.
- dmurray 8y agoSound waves are often compared to water waves in this way. The water just moves up and down, and the horizontal movement is (mostly) an illusion. But everyone knows intuitively that the water is moving horizontally at least a little bit. Some ocean water gets left on the beach or the boardwalk, or perhaps your toy or ball gets swept out to sea on the waves. Is this the right analogy, or are they talking about something different?
- petters 8y agoThe water moves in circles/ellipses.
- Majromax 8y agoNot in closed circles/ellipses. With finite wave amplitudes, a fluid parcel in wave motion experiences Stokes Drift (https://en.wikipedia.org/wiki/Stokes_drift https://en.wikipedia.org/wiki/Stokes_drift). In water, this effect arises because the fluid is deeper at the crest of the wave than at the trough, and wave velocities are faster in deeper water. The fluid parcel moves up -> forwards quickly -> down -> backwards more slowly. I'm curious about whether the researchers here have demonstrated a similar effect for sound waves. Pressure waves have similar dynamics (with faster particle movement at lower pressures), and the researchers mention that this is a finite-amplitude effect.