 Eternal bouncing models qualitatively similar to the pre-big-bang scenario have been proposed earlier, either on the basis of the relativistic field equations or on the idea of a plasma universe. According to the Swedish physicist Hannes Alfvén, a Nobel laureate of 1970 who developed the latter idea, the plasma universe was an alternative to the theistic big bang theory. Since none of the models considered in this section operate with an absolute beginning, they may seem to be problematic from a theistic point of view. However, the theist can always appeal to perpetual divine creation, just as in the case of the steady-state universe.