With the New Year just a few days away, I’m thinking about time. Why must time move in one direction — forward? Why isn’t it reversible? Why can’t the future become the past? Because it just can’t, you say impatiently, already bored by the naiveté of the question.
The fundamental physical laws of nature such as gravity, electricity and magnetism are reversible. Even molecular collision is reversible. So why aren’t the phenomena that happen according to these laws of physics reversible — the phenomena that constitute our perception of time?
How do we resolve this paradox?
In Richard Feynman’s lecture, “The Distinction of Past and Future,” he explains how the laws of physics do not have a obvious relevance to the world as we experience it. Don’t know Feynman? He’s a professor famous for a series of lectures taped by the BBC at Cornell University in 1964. Last July, Bill Gates made these lectures publicly available through a Microsoft Research initiative called Project Tuva.
But let’s get back to the question of time: How can it be that our experience of time is so different from the fundamentals that constitute it?
To me, this is similar to the false intuition that a heavy object should fall more swiftly than a light one. It doesn’t. (Gravity, unlike your mother, is blind to how much something weighs, though it might agree that you look fat in those pants.) If you drop a book and a fork, they’ll hit the ground at the same time, even though you might think the heavier object — the book — should hit first. I’m always guilty of thinking this way. I was reminded of my wrong intuition recently as I was reading about Newton’s Second Law of Motion in The Great Equations. (At least Aristotle was wrong, too.)
Why do we get these things wrong? Because, as Feynman explains at the end of “The Distinction of Past and Future,” the world is both fundamentally simple and tremendously complex, “to stand at either end and to walk out off the end of the pier only, hoping out in that direction is the complete understanding, is a mistake.” In other words, maybe our (incorrect) intuition that heavier objects should hit the ground first comes from the fact that they hit the ground harder, and we connect this to the idea of velocity, which takes us around to the idea of heavier falling faster. Makes sense, but it’s wrong. We’re standing at the wrong end of the pier and can’t see what’s really happening.
As for time, what phenomenon could be more straightforward: a simple line of actions connected dot to dot, the single constant in our lives, irrevocable. So why do we wonder and wish to make the past the future — to jump backwards, branching out in a new direction? Because our knowledge of time is complex, our understanding of what could have happened instead as real to us as the memory of what did.
Remorse and regret, hope and aspiration — these complex thoughts and emotions spring from our perception of time passing. They are as real as the law of gravity and sometimes so heavy they sink you into a hole, other times so light you feel as if you’re floating. At this time of year, it’s nice to be reminded that there’s always the other end of the spectrum; it exists all the time. You don’t have to wait until next year for things to turn around because in some way they already are.
But enough of this. All I really wanted to say was Happy New Year! Simple.