  Is Newton's gravity sufficient to handle the weakly nonlinear evolution
stages of the cosmic large-scale structures? Here we resolve the issue by
analytically deriving the density and velocity power spectra to the second
order in the context of Einstein's gravity. The recently found pure general
relativistic corrections appearing in the third-order perturbation contribute
to power spectra to the second order. In this work the complete density and
velocity power spectra to the second order are derived. The power transfers
among different scales in the density power spectrum are estimated in the
context of Einstein's gravity. The relativistic corrections in the density
power spectrum are estimated to be smaller than the Newtonian one to the second
order, but these could be larger than higher-order nonlinear Newtonian terms.
