-- compare Example 6.1.
Does that mean there is a 50 % chance that our universe will get
at least twice as old as it is now? Not necessarily, if the computation
of its state at the n-th time step (local time)
requires more than O(n) time.
As long as there is no compelling contrarian evidence, however, a reasonable guess would be that our universe is indeed among the fastest ones with O(1) output bits per constant time interval consumed by algorithm FAST. It may even be ``locally'' computable through simple simulated processors, each interacting with only few neighbouring processors, assuming that the pseudorandom aspects of our universe do not require any more global communication between spatio-temporally separated parts than the well-known physical laws. Note that the fastest universe evolutions include those representable as sequences of substrings of constant length l, where each substring stands for the universe's discretized state at a certain discrete time step and is computable from the previous substring in O(l) time (compare Example 1.1). However, the fastest universes also include those whose representations of successive discrete time steps do grow over time and where more and more time is spent on their computation. The expansion of certain computable universes actually requires this.
In any case, the probability that ours will last 2n times longer than it has lasted so far is at most 2-n (except, of course, when its early states are for some reason much harder to compute than later ones and we are still in an early state). This prediction also differs from those of current mainstream physics (compare [#!Gott:93!#] though), but obviously is not verifiable.