Browse all


Philosophy, sociology and religion

Philosophy, sociology and religion

(Courtesy: iStock/deimagine)
05 Jul 2018 Robert P Crease
Taken from the July 2018 issue of Physics World

Robert P Crease wonders if there is a topic murkier than time

In ordinary experience, time is permanently present in the world. Continuous and flowing, it moves in one direction – from past to future, the border being a momentary “now”. Thanks to this movement, humans remember, perceive, plan and act consciously and deliberately. Humans do so as individuals and in groups, transforming themselves and the world, creating culture, history and science. Even doing physics, in which you creatively use what you already know to make fresh discoveries, requires living time this way.

Yet many physicists declare such everyday experience of time a mirage. “For we convinced physicists,” Einstein wrote, “the distinction between past, present, and future is only an illusion, however persistent.” Brian Greene wrote in the New York Times that “the temporal categories of past, present and future” are “subjective” and that the “everyday conception of time appears illusory.” One chapter in theoretical physicist Carlo Rovelli’s book, Reality Is Not What It Seems, was even entitled “Time does not exist.”

The fog of time

Rovelli appears less dismissive in his new book The Order of Time (for more information on it see this interview). Time can be approached in two ways, he writes – either as something foundational to human experience or as foundational to the world itself. He describes the former as a “fog” or “blur” that results from us seeing nature at a distance. Sure, this fog is important in the sense that it opens up a space or dimension for us to be human – “we are this space”, he writes – and to encounter the cosmos. But time, he insists, is not a part of that cosmos. It is a mere “epiphenomenon”, like seeing the Sun “set”.

Rovelli admits that time is “perhaps the greatest remaining mystery”. But physics promises to dispel that mystery, for it sees the difference between the two approaches and studies “the nature of time free from the fog caused by our emotions”. To help us picture this dual view of time, Rovelli invokes Paul McCartney’s song Fool on the Hill, who – as Rovelli puts it – “sees the Earth turn when he sees the setting sun”. Just as the fool can appreciate something deep – the Earth spins – from watching the Sun go down, so we ought also to be able to perceive the  “profound structure of the world [even though] time as we know it no longer exists”.

Rovelli’s book seems to leave room for the everyday experience of time. Still, he does not call that kind of time fully real in the sense of belonging to the ultimate elements of the world that physicists study. Everyday time is not an illusion, he thinks, but not real either. One might compare his approach with that of the philosopher Immanuel Kant, who said that time is “empirically real”, encountered and measurable in the world we live, yet “transcendentally ideal”, or part of that world only insofar as it is a precondition for having any experience of the world at all – a feature of the mind’s programming software if you like.

But experienced time comes first, even before the distinction between it and physicists’ time. Without experienced time, humans lack any encounter with the world at all, from storms to supernovae. The world is disclosed in, and thanks to, experienced time, which therefore has a kind of priority over what appears.

For centuries, philosophers and scientists have been tempted to seek some seemingly permanent, unchanging stuff in experience – quantum fields, say – that give rise to everything else, including human experience, and name this the “real”.  The trouble with the “reality trick” is not just that we keep changing our minds about the fundamental stuff. It also downgrades the importance of everything else, most notably our lived experience. Rovelli seems to recognize this in a chapter on how language can promote certain erroneous assumptions about reality and existence. Still, it is all too tempting to revert to language that suggests that storms and supernovae are not real but merely epiphenomena.

To study a melody, for instance, you have to experience it. Only after that experience can we break it down and use a clock to say that such and such note occurred at 17 or 92 seconds into it. Only because of a continuous qualitative movement is there a unified melody in the first place to which that note belongs. This upsurge of reality was dubbed “duration” by Henri Bergson, who regarded it as the font of the abstract, homogenous time measured by clocks; Martin Heidegger described something similar under the name of “temporality”. This is not wordplay, but part of an attempt to describe fundamental features of the world evocatively that is not merely “poetic” but indicative of qualities not otherwise accessible.

The critical point

You can’t explain time by putting physicists in charge of “what time really is” and then trying to stitch this together with experienced time. That inevitably results in experienced time having a secondary status – discussed only in humanities courses that get axed from the curriculum when the next budget crisis hits. The task for philosophers of time is to explain that physicists’ conceptions of time are highly selective, mathematized ideas that are useful, but grow out of human concerns that arise in experienced time.

You can’t explain time by putting physicists in charge of “what time really is”

“He never listens to them,” runs the final verse of McCartney’s song. “He knows that they’re the fools.” That’s where McCartney’s lyrics annoy me, for I hear the reality trick being played yet again. Yes, I know the guy on the hill can see simultaneously both the Sun setting and the Earth spinning, which is good. And I know I’m over-reading the song. But the lyrics claim superciliously that this guy sees deepest of all, and that those who see otherwise are deluded. To clear up the mystery of time, and many other issues dividing philosophers and physicists, we must stop insisting there is just one right way to see these things. That makes fools of us all.

Related journal articles from IOPscience


Copyright © 2018 by IOP Publishing Ltd and individual contributors
bright-rec iop pub iop-science physcis connect