On Oct 17, 4:32*pm, "Szczepan Bialek" wrote:
*"K1TTT" ...
On Oct 17, 9:28 am, "Szczepan Bialek" wrote:

"K1TTT"
...

water flow and water waves are NOT good analogs for electromagnetic

waves. the only common part is that some part of the solution of
their equations includes a sine or cosine function.

Each waves are the same. They transport mass and energy. They never are
harmonic.
S*
no, waves can transport energy without mass. *photons have not rest

mass, only energy... look that up in your favorite wikipedia. *sound
waves require mass, but don't have to transport it, just move it back
and forth around a point, thus they move energy without net movement
of mass.

So read the Wiki:
"For a pure wave motion in fluid dynamics, the Stokes drift velocity is the
average velocity when following a specific fluid parcel as it travels with
the fluid flow. For instance, a particle floating at the free surface of
water waves, experiences a net Stokes drift velocity in the direction of
wave propagation.
More generally, the Stokes drift velocity is the difference between the
average Lagrangian flow velocity of a fluid parcel, and the average Eulerian
flow velocity of the fluid at a fixed position. This nonlinear phenomenon is
named after George Gabriel Stokes, who derived expressions for this drift in
his 1847 study of water waves."

This nonlinear phenomenon is in each real wave. In texbooks are a paper
waves - for kids. They are linear and symmetric.

"just move it back and forth around a point" is a simplification necessary
in schools.

S*

ah, but that requires fluid flow. electromagnetic waves do not
require fluid flow or they could not travel at c. There may be some
analogous phenomena in plasma where you can get non-linear effects but
they would not propagate at c, they would be at some much smaller
velocity.