3.9.18 Horizon Problem
Since the Universe has a finite age, and light travels at a finite speed, so information can’t travel faster than light, this means any two regions of space that are not in causal contact are completely separated and can not interact. Yet the Universe appear to be homogeneous in all directions, while there is no mechanism to cause the various separated regions to have the same temperature, as observed by the isotropy of the background radiation.
As we discussed in section 6.4, the cosmic inflation models provide a resolution to this apparent inconsistency, where a homogeneous and isotropic scalar energy field dominates the Universe at some very early period, before baryogenesis, then during inflation, the Universe undergoes exponential expansion, and the particle horizon expands much more rapidly than previously assumed, so that regions presently on opposite sides of the observable Universe are well inside each other’s particle horizon.
According to the perpetual re-creation, since the universe, no matter how large it could be, is re-created sequentially in the inner levels of time, all the states are synchronized before they appear as one instance in the normal time level. This would not have been conceivable without taking rigid space as flowing time in the inner level, and thus the outer time becomes latent to it.