Dr. Neville Jones wrote: > As far as I understand it, the law of conservation of angular > momentum applies to rigid bodies. Not to liquids and not to gases. > The reason for this necessity is that imparting a torque to a > molecule in a rigid body affects the whole body, which is not the > case with the other two states. The law of conservation of angular momentum applies to everything in any closed system. Remember that momentum (angular or rectilinear) is proportional to mas and velocity. If you impart a certain momentum on a molecule of a fluid it has very little mass and will have a correspondingly high velocity. If that molecule is part of a rigid body then the mass of the object moved is much greater and the velocity therefore much less. In both cases the momentum is the same. The single molecule is just a very small rigid body. If it is emersed in many other molecules then it will quickly collide with another imparting some of its momentum to it. Many of these collisions will cause the momentum to be spread out amongst many molecules of the fluid. In principle you could treat each collision as a rigid body collision that conserves angular momentum but we instead treat them statistically and call this energy of motion transferred to all these molecules heat. But CAM is still preserved throughout. > Consider the World, without an atmosphere, spinning in a vacuum. If > we then wrap a non-moving atmosphere around it, that atmosphere will > serve to damp the spin of the World. Do we agree that in this > scenario the orld will slow down and the atmosphere will start to > turn? Yes, until they reach equillibrium at which point they will rotate together with no friction. But the angular momentum at the beginning will be the same as at equillibrium. The earth will have slowed, the atmosphere will have sped up. > On the assumption that we do, then where we disagree is in what > follows on from this. There is no way that the World will ever speed > up again, right? Well we could shoot off heavy missiles easterly at escape velocity to speed the earth up again, but the total angular momentum of the missiles, earth and atmosphere would still be the same. > We have now a World-atmosphere "closed system," in > your terminology, that you will say has reached some sort of > equilibrium in terms of its angular momentum. What I am saying is > that this is not a "closed system," in the sense you infer, but an > interactive system between a rotating spherical object (not even > rigid, because of its excessive water content), surrounded by a > gaseous envelope. If you only consider everything on the earth including the atmosphere and anything that might be flung off, including radiating photons, then it is a closed system and angular momentum will be preserved. If you're saying that the earth system is not closed because it looses energy through radiation then this is true (and it also recieves energy from the sun) - but the energy lost is radiated pretty much equally in all directions and the total angular momentum of this radation is therefore zero and does not affect the angular momentum of the earth system. > The crux of the difference between us is this: you maintain an > equilibrium because of the "closed system," and I accept that you > have "conventional" physics on your side, insofar as that is the > "party line." I maintain that the World would constantly be losing > the energy that it possessed as a result of its rotation, to an > atmosphere which would heat up due to this friction and dissipate > this extra energy by radiating most of it out into space. You're confusing conservation of energy with conservation of angular momentum as above. Regards, Mike.