The Arrow of Time

Sean Carroll has a curious speculative article in Seed magazine about the arrow of time. He writes that, at the lowest level, physical laws don't discriminate between past and future and so it is puzzling that we can use eggs to make an omelet but we can't reverse the process and use an omelet to get eggs. One could say that the arrow of time emerges as a property of the macroscopic universe. Scientists use the concept of entropy to explain its inexorable march towards total disorder and final emptiness. This points to an asymmetric situation where the entropy is very low at the beginning of the universe and very high at the end.

This is the usual story. Now comes the speculation. He argues that perhaps, on a larger scale, time does maintain its symmetry and the entropy of the universe is high in both ends. A universe with very high entropy is basically empty and he suggests that in this case quantum fluctuations could generate a (very unlikely) situation where the amount of dark matter was just right to cause inflationary expansion of a minute region. This, he continues, would be consistent with the Big Bang view of the universe. The difference is that this unlikely situation could occur multiple times and generate multiple "baby universes" or "multiverses". I think other scientists have suggested similar views, but he goes on to speculate that in some of these baby universes the arrow of time could be running backwards.

Now, that is interesting! Would such universes support intelligent life? Would their inhabitants know that their time was running backwards? Is our own time running backwards in some non-human scale?