  A cosmological model based on Kaluza-Klein theory is studied. A metric, in
which the scale factor of the compact space evolves as an inverse power of the
radius of the observable universe, is constructed. The
Freedmann-Robertson-Walker equations of standard four-dimensional cosmology are
obtained precisely. The pressure in our universe is an effective pressure
expressed in terms of the components of the higher dimensional energy-momentum
tensor. In particular, this effective pressure could be negative and might
therefore explain the acceleration of our present universe. A special feature
of this model is that, for a suitable choice of the parameters of the metric,
the higher dimensional gravitational coupling constant could be negative.
