In article ,
Beryl wrote:

Alan Baker wrote:

It's like the downwash argument. You can say "IT DOESN'T MATTER", when
people argue that the air behind an aircraft is not deflected downward,
but it *does* matter. Having an accurate understanding of the physical
processes of flight matters.

It isn't really deflected downward, not for long anyway. It's churning
in a torus. Like a smoke ring.

No.

It really *is* deflected downward.


The edges of the deflected area churn, and the air that is deflected
ends up getting diffused among all the other air below *it*, but it
really is deflected downward.

And eventually, that downward deflection makes it way until it -- very
diffusely -- impacts upon the surface of the earth. That is the only
thing that finally stops it.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg