  Starting from the classic Friedmann-Robertson-Walker theory with big bang it
is shown that the solutions of the field equations can be extended to negative
times. Choosing a new cosmic time scale instead of proper time one achieves
complete differentiability of the scale factor and of suitable thermodynamic
quantities equivalent to pressure and energy density. Then, the singularity of
big bang manifests itself only by the vanishing of the scale factor at time
zero. Moreover, all solutions of the field equations are defined for all times
from -infinity to +infinity. In a separate chapter the horizon structure of the
extended theory is studied. Some weak assumptions guarantee that there are no
horizons. Hence, the horizon problem in a strict sence disappears. An intensive
discussion of the results is given at the end of the paper.
