  During the evolution of density inhomogeneties in an $\Omega=1$, matter
dominated universe, the typical density contrast changes from $\delta\simeq
10^{-4}$ to $\delta\simeq 10^2$. However, during the same time, the typical
value of the gravitational potential generated by the perturbations changes
only by a factor of order unity. This significant fact can be exploited to
provide a new, powerful, approximation scheme for studying the formation of
nonlinear structures in the universe. This scheme, discussed in this paper,
evolves the initial perturbation using a Newtonian gravitational potential
frozen in time. We carry out this procedure for different intial spectra and
compare the results with the Zeldovich approximation and the frozen flow
approximation (proposed by Mattarrese et al. recently). Our results are in far
better agreement with the N-body simulations than the Zeldovich approximation.
It also provides a dynamical explanation for the fact that pancakes remain thin
during the evolution. While there is some superficial similarity between the
frozen flow results and ours, they differ considerably in the velocity
information. Actual shell crossing does occur in our approximation; also there
is motion of particles along the pancakes leading to further clumping. These
features are quite different from those in frozen flow model. We also discuss
the evolution of the two-point correlation function in various approximations.
