Several new results are obtained for the classical problem of inertial wave
s in a rotating fluid sphere which was formulated by Poincare more than a c
entury ago. Explicit general analytical expressions for solutions of the pr
oblem are found in a rotating sphere for the first time. It is also discove
red that there exists a special class of three-dimensional inertial waves t
hat are nearly geostrophic and always travel slowly in the prograde directi
on. On the basis of the explicit general expression we are able to show tha
t the internal viscous dissipation of all the inertial waves vanishes ident
ically for a rotating fluid sphere. The result contrasts with the finite va
lues obtained for the internal viscous dissipation for all other cases in w
hich inertial waves have been studied.