Bob Cain wrote:



Laurence Payne wrote:

On Tue, 17 Aug 2004 11:25:12 -0700, Bob Cain
wrote:


Because there is a real difference. Air can't carry the DC component
of velocity but it can carry any time varying component.



I guess DC offset in air is barometric pressure?


Right, and a constrained piston can't change it.

Drop the "constrained" qualifier.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein