  If the split, asymmetric molecular spectral line profiles that are seen in
many starless cores are interpreted as indicative of global collapse or
expansion of the core then one possible implication is that most starless cores
have short lifetimes on the order of the collapse or sound crossing time scale.
An alternative interpretation of the line profiles as indicative of
perturbations on an underlying equilibrium structure leads to the opposite
implication, that many cores have long lifetimes. While evidence suggests that
some cores are collapsing on a free-fall time scale, we show that observations
of some other starless cores can be reproduced by a model of non-radial
oscillations about the equilibrium configuration of a pressure-bounded,
thermally-supported sphere (Bonnor-Ebert sphere). We model the oscillations as
linear perturbations following a standard analysis developed for stellar
pulsations and compare the column densities and molecular spectral line
profiles predicted from a particular model to observations of the Bok globule
B68.
