Let's today tie together some thoughts that've been explored in the previous two posts.
There are two theories as to the nature of time. The first, the A theory, is the common sense view that time is like a flowing river that carries the events of our lives past us like the stream carries water past a person standing in the stream. Future events lie upstream, heading toward us, and the past is downstream, flowing away from us. Events, on this view, are said to have tense - past, present and future.
Another theory, more counterintuitive but nevertheless popular with many, maybe most, philosophers and scientists, derives from Einstein's theory of the relativity of time. On this view, called the B theory, every event that has ever occured is happening somewhere now. Our consciousness somehow moves from event to event, but time itself is static and tenseless.
We employed the analogy in Saturday's post of a movie that's been burned onto a DVD. Every event in the movie, every moment, is present simultaneously, but is only "read" off the DVD by the player in a "one moment at a time" sequence. On the B theory, then, our birth, high school graduation, marriage and death are all in some sense happening now.
One of the interesting consequences of this view, although I don't think I've ever seen it alluded to, is that if it accurately describes the way things are, if the flow of time is an illusion, then it would seem to make little sense to ask how old the universe is.
Claims that the universe is 13.7 billion years old should really be understood as claims about how old it appears to us to be. If every event exists simultaneously somewhere on the temporal DVD, then the apparent lapse of 13.7 billion years, or any "length" of time, is simply the illusory consequence of the way our minds process events, but the objective age of the universe, if there is one, is inscrutable.
The universe - its birth, life and death - potentially came into being simultaneously, or at least in no particular order, like the beginning and end of a movie could theoretically be impressed upon the DVD instantaneously.
This is not to say that this is how things actually are. It's only to say that it seems like a plausible consequence of the B theory of time.
Thus, if either time is a subjective phenomenon, a consequence of our mental architecture as we discussed on Friday, or if the B theory is true it would follow that the question of the age of the universe is moot.
If that's so, then one of the major points of contention between those who believe the universe is relatively young, on the order of ten thousand years old, and those who believe it is much older is also moot. The universe could be scarcely any age at all even though there's plenty of empirical evidence that gives it the appearance of being almost 14 billion years old.
It all depends on the actual nature of time.
