Why Can’t You Remember Your Future? Physicist Paul Davies on the Puzzlement of Why We Experience Time as Linear
The curious question of how and whether we can tell the difference between an experience and the memory of an experience.
By Maria Popova
“If our heart were large enough to love life in all its detail,” French philosopher Gaston Bachelard wrote in his 1932 meditation on our paradoxical experience of time, “we would see that every instant is at once a giver and a plunderer.” Nowhere is this duality of time more disorienting than in the constant mental time travel we perform between what has been and what will be in order to anchor ourselves to what is. As our lives tick on, gradually robbing the future of potential and robbing the past of relevance, we trudge along the arrow of time dragging with us this elusive curiosity we call a self — an ever-shifting packet of personal identity, mystifying in how it links us to our childhood selves and misleading in how it maps out our future selves.
That puzzlement is what Australian theoretical physicist Paul Davies explores in a wonderfully mind-bending passage from his altogether terrific 1995 book About Time: Einstein’s Unfinished Revolution (public library), which embodies my three criteria for what makes a great science book.
When I was a child, I often used to lie awake at night, in fearful anticipation of some unpleasant event the following day, such as a visit to the dentist, and wish I could press some sort of button that would have the effect of instantly transporting me twenty-four hours into the future. The following night, I would wonder whether that magic button was in fact real, and that the trick had indeed worked. After all, it was twenty-four hours later, and though I could remember the visit to the dentist, it was, at the that time, only a memory of an experience, not an experience.
Another button would also send me backwards in time, of course. This button would restore my brain state and memory to what they were at that earlier date. One press, and I could be back at my early childhood, experiencing once again, for the first time, my fourth birthday…
Nobel-winning psychologist Daniel Kahneman addressed this perplexity in his model of the experiencing self and the remembering self, but for Davies the more interesting question deals not with the pure psychology of the experience but with how the accepted physics of time, seeded by Einstein’s relativity theory, gives shape to that psychological experience. He returns to the larger questions arising from his childhood thought experiments:
With these buttons, gone would be the orderly procession of events that apparently constitutes my life. I could simply jump hither and thither at random, back and forth in time, rapidly moving on from any unpleasant episodes, frequently repeating the good times, always avoiding death, of course , and continuing ad infinitum. I would have no subjective impression of randomness, because at each stage the state of my brain would encode a consistent sequence of events.
The striking thing about [such] “thought experiments” is, how would my life seem any different if this button-pushing business really was going on? What does it even mean to say that I am experiencing my life in a jumpy, random sort of manner? Each instant of my experience is the experience, whatever its temporal relation to other experiences. So long as the memories are consistent, what meaning can be attached to the claim that my life happens in a jumbled sequence?
In the remainder of the thoroughly satisfying About Time, Davies goes on to probe the answer to this question by examining how the history of human thought, from St. Augustine to Einstein, has left us with a model of time that simply doesn’t reflect the nature of experience, and what we can expect from the evolution of science as we reach for more complete models of this timelessly puzzling dimension of reality.
Complement it with T.S. Eliot’s beautiful ode to the nature of time and Virginia Woolf on the elasticity of time, then revisit the historic debate that shaped our modern understanding of time.
Published January 25, 2016