to an atmosphere which would heat up due to this friction and dissipate this extra energy by radiating most of it out into space. Neville, what actually is the ratio of energy in to energy out from space, the sun of course being the major contributor. I thought we were gaining heat. Perhaps it varies. As a part of the point you raised fluid versus solid cloak, couldn't there be a stable mean. a resultant of all the factors' This is all academic of course, as it is to me highly probable, I should say certain if I use that awful C word, that the world doe not spin, and neither does the atmosphere except in a cyclone. We should be looking for other reasons for the clockwise/anticlockwise rotation of cyclones and hurricanes....Also for the same reason, why does the gyro of which the faucault pendulum is but a part, rotate one revolution per day with the sun... Philip.