[I met Dan Falk early last year at the SciBar Camp in Toronto, and later again at PI's multiverse conference. As most science writers I've met, he brings a cheerful interest in whatever the so-called edge of research currently discusses that is impossible to maintain if you happen to dance on that edge. He has written two books, neither of which I read, but I have occasionally come across his articles in the Globe and Mail which are always a pleasure.]
What better time than the start of a new year to reflect on the nature of time. (Thanks, Sabine, for letting me post here on this subject!)
Today’s atomic clocks can measure time to within a fraction of a billionth of a second per day – so well, in fact, that they reveal the irregularities in the earth’s rotation. As a result, we have to insert a “leap second” into the day every few years, as we did recently on the evening of Dec. 31 – a subject I discussed in an essay in the Toronto Star.
The technology that allows for this ultra-fine dissecting of time is indeed impressive. Yet our science – and perhaps our philosophy – may have some catching up to do. Indeed, one can legitimately ask: What is it, exactly, that these clocks are measuring?
I’ve given a lot of thought to this question of the last few years, as it lies at the heart of my latest book, In Search of Time: Journeys along a Curious Dimension (McClelland & Stewart, 2008).
Physics – perhaps surprisingly – has less to say on the subject than we might expect. Einstein’s relativity tells us all about the rates at which clocks tick: We know that a clock whizzing by at high speed will be seen to tick more slowly than one that appears to be stationary; that a clock in a strong gravitational field will tick more slowly than one on the surface of the earth.
Yet Einstein’s equations do not distinguish past from present or present from future. Just as with Newtonian physics, they say nothing of time’s “flow,” its relentless passage. Indeed, physics considers all moments to be alike, with space and time laid out in a vast, static “block.”
But this is not how we experience time: We seem to inhabit a single moment, a fleeting “now.” The explanation for this, it seems, may lie not in physics but in psychology or philosophy; indeed, many thinkers suspect that time’s alleged flow – this “moving now” – may be little more than an illusion, a trick of the mind.
Einstein once spoke of this dilemma. His friend, the philosopher Rudolf Carnap, recalls Einstein admitting that “the experience of the Now worried him seriously.” The experience of the Now, Einstein told him, “means something special for man, something essentially different from the past and future, but that this important difference does not and cannot occur within physics.”
And so the question remains, where does this difference occur? Why do we feel that time passes? Perhaps it will take an intellect even greater than Einstein’s to illuminate the mystery of time’s apparent flow.