  General relativity predicts a singularity in the beginning of the universe
being called big bang. Recent developments in loop quantum cosmology avoid the
singularity and the big bang is replaced by a big bounce. A classical theory of
gravitation in flat space-time also avoids the singularity under natural
conditions on the density parameters. The universe contracts to a positive
minimum and then it expands during all times. It is not symmetric with regard
to its minimum implying a finite age measured with proper time of the universe.
The space of the universe is flat and the total energy is conserved. Under the
assumption that the sum of the density parameters is a little bit bigger than
one the universe is very hot in early times. Later on, the cosmological model
agrees with the one of general relativity. A new interpretation of a
non-expanding universe may be given by virtue of flat space-time theory of
gravitation.
