In article ,
Scott wrote:

Alan Baker wrote:
In article ,
Scott wrote:

Alan Baker wrote:

Observation can lead you astray: and that is clearly the case here if
you actually think that air can *pull* on a surface.

Why can't air PULL on a surface? Air is made up of molecules.
Molecules have mass. Anything with mass can attract anything else with
mass, can't it?

Gravity?

You're not serious.

Anti-gravity in this case. If air can push something, why can't it pull
something?

Because the push is caused by the impact of countless air molecules with
the surface of wing. If those collisions fall to zero (i.e. in a perfect
vacuum) then there is zero push.

But there is no set of circumstances that can make the number of
collisions be negative.

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