Robert, I ignored your question? A deplorable suggestion! I do not believe that planetary orbits are elliptical. Rather, I support the deferent and epicycle model of Apollonius of Perga. Planetary motion in this scenario is circular and at a uniform rate. You state that, "Another example would be the upward path of a projectile, which is always decelerating. The principal reason is gravity, which theogeocentrists (us) replace with the plenum." However, I would not attribute this resistance to any force of the plenum/firmament, but would attribute it in the conventional way to the World's gravitational attraction. In Christ, Neville. Robert Bennett <robert.bennett@xxxxxxx> wrote: Dear Dr. Jones, I don't have the time to make everything rhyme... I would say re-adjust at the surface..... a flexible plenum. The reason for this inquiry line about plenum boundary is to establish where the properties of the plenum end. Once we know the plenum properties, we can test for differences across the boundary with experiments underwater (in a submarine?) - which we agree on - or underground - which is now undecided. You seem to use frictionless to mean 'undetectable'. Again a brief exposition would help. One example of slowing down would be planetary orbits (assuming you believe they are ellipses). In half the orbit the planet is slowing down. Along with Newton and Kepler I would not term this 'friction' when there is no visible contact with anything. Another example would be the upward path of a projectile, which is always decelerating. The principal reason is gravity, which theogeocentrists (us) replace with the plenum. The plenum channels I prefer to address when the proper foundation has been built. BTW: You didn't address all my Qs, mostly the ones I said were for later! Thanks for entertaining my thoughts. Pax Christi, Robert Send instant messages to your online friends http://uk.messenger.yahoo.com