This book review was taken from the September issue of The Critic. To get the full magazine why not subscribe? Right now we’re offering three issue for just £5.

A friend of mine has a brilliant idea. She thinks we should celebrate Christmas only during leap years. True, her children, for whom 12 months is an age, don’t think much of this suggestion. But my friend, like me, is at that age where time is beginning to speed up. Christmas might well come but once a year. But when a year comes and goes as quickly as the Christmas vac once did, it begins to feel like you’re buying presents and roasting turkey every other week.

The conventional explanation for this telescoping of temporal experience — attributed by William James to the nineteenth-century French philosopher Paul Janet, one learns from Joseph Mazur’s dumb-foundingly good The Clock Mirage — is arithmetical. To a ten-year-old child a year is a tenth of her existence, and thus feels like something of a stretch. For someone who’s twice her age a year is only a twentieth of the time they’ve already had, and by the time you get to 60, well, I’d say it doesn’t bear thinking about were it not for the fact that thinking about it is all you do once you get to a certain age …

But hold on a minute, says Mazur, who is a mathematician by training, but knows his way around physics and philosophy. Things are rather more complicated than that. To be sure, life in general does seem to speed up as you age. But particular moments can slow or even still the flow. The passing of a partner or a parent or, God forbid, a child will put the brakes on time no matter how old you are.

That’s because, Mazur argues, these are — with luck — one-off events and the longer you’ve been around, the fewer one-offs come your way. Your first fall, your first car, your first kiss — these are, as Mazur says, “landmarks” on your life. But the older you get, the rarer such landmarks are. Life becomes more mundane, more samey. The days seem to roll into one another, simply because there’s very little to demarcate them from one another.

then again, there are objective reasons for the speed of subjective time changing as we age. Just as your metabolism slows the older you get, so, it turns out, does your body clock decelerate too. As Mazur points out, older people (not always consciously, and not always for physical reasons) tend to move more slowly than younger people. But along with the physical slowing of your sense of balance, your reaction times, your vision, your hearing, he says, so the movement of time itself seems to slow in unison.

Little wonder that psychologists have shown that the accuracy of second-counting — one little second, two little seconds, etc — decreases with age. Over a three-minute period, younger people can count down the seconds almost perfectly. Older people, on the other hand, can be out by as much as forty seconds — meaning that if they counted seconds for an hour they’d think the task done with around the 47-minute mark.

It sounds paradoxical, but it’s that slowing of the older person’s body clock that leads to their faster counting — and their feeling that the rest of the world is speeding up. Relativity is all.

Still, back in the objective world, Newton’s suggestion that “absolute, true, mathematical time, of itself, and from its own nature, flows equably without relation to anything external” still holds water, doesn’t it? Yes, but only in the sense that a colander does. It turns out that Heisenberg was nearer the mark when he argued that time is nowhere near as continuous as it seems to be to us.

Taking his cue from Zeno and his paradox about the arrow that never arrives because it’s always a fraction of the original distance away from its destination, he argued that, like light, time isn’t an endless continuity. (Intriguingly, Mazur points out, though the paradox arises from a false premise, Zeno had nevertheless intuited what physicists wouldn’t prove for another 2,300 years or so — that space and time are a seamlessly interlinked manifold.)

Rather, Heisenberg said, light is made up of tiny particles (he called them quanta, though Mazur, taking his inspiration from the word photon, suggests they might better be called chronons). Particles so tiny, Heisenberg said, that the smallest discrete unit of time is around 10^-26 seconds. Not small enough? Try Max Planck, who postulated a unit of time that lasts 5.39 x 10^-44 of a second. Not long enough to boil an egg, perhaps, but enough time for light in a vacuum to travel one Planck length — around 6.3 x 10^-34 of an inch.

Talking of travel, as Mazur often is, according to Newtonian theory if two people at the same point — call it A — at the same time — call it B — go off wandering simultaneously but independently, before returning to B at an anointed hour, then they will each have wandered for the same amount of time. Except that they might not have. Channelling Einstein, Mazur asks us to imagine two identical clocks — A and B, natch. A stays put, but B goes off a’roving, at a constant speed, along a curve that eventually brings it back to base. Both clocks register B’s journey time — but B registers it as being smaller than A does. What’s more, the faster B goes a’roving, the greater the time disparity that the two clocks will register. That’s because time, isn’t absolute but relative. Like beauty, it’s in the eye of the beholder.

All of this means that the first word in Mazur’s book — “Now” — has no objective meaning. Thanks to Einstein, we, er, now know that there is simply no now that we can ever agree upon. Indeed, what we call now, Einstein called “a stubbornly persistent illusion”. Stubborn is right, as I’m sure you agree.

So try thinking of it like this. If you’re talking to a friend across the room, you see him not as he is at this precise point in time but as he was a moment ago — to be precise, at that moment when the light you are seeing bounce off him began travelling from him towards you. However infinitesimally different, that is, your “now” is his “then”.

Now — boy, but that word gets everywhere — let’s scale that up some. As I write it’s early June, 2020. But were I to look through a sufficiently powerful telescope at a star whose light takes 75 years to reach the earth, I shouldn’t be seeing that star as it is today. I’d be seeing it as it was in 1945. In fact, I could be looking at something that no longer exists. That star could have burned out at some point during the past three-quarters of a century. And even if it is still in existence, it probably won’t be in the same place.

He covers just about every other theorist of time with grace and wit, explains why time speeds up when you’ve got a fever

Now — there I go again — turn this on its head. Imagine that up there on that star is somebody or something — let’s call him a little green man —with a telescope powerful enough for him to look at life here on earth. What would he see if, in our summer of 2020, he looked through his telescope at our world? Well, he wouldn’t see me — and unless you’re over 75 he probably wouldn’t see you either. Because he wouldn’t be looking at our world today. He’d be looking at our world in 1945.

So he might see crowds dancing in Piccadilly Circus at the war’s end. He might see Churchill and Attlee campaigning in the general election. He might see Hiroshima go up in flames. As the poet said, “Time present and time past / Are both perhaps present in time future / And time future contained in time past.”

Perhaps because he writes poetry himself (The Clock Mirage is studded with his verse), Mazur doesn’t mention Eliot. Nor, surprisingly, does he mention Heidegger or Husserl or Merleau-Ponty — and Bergson crops up in passing on only a couple of occasions.

Still, he covers just about every other theorist of time with grace and wit, explains why time speeds up when you’ve got a fever and slows down when you think you’re in danger, and he even finds the time to talk to everyone from city traders to truck-drivers about their very different experiences of clock-watching. They offer much food for thought, though for my money the most nourishing ideas come from a guy called Clint Barnum.

“Time,” Clint tells Mazur, “is linked in some way to consciousness. It is the measure of life. We are conscious beings placed in a physical world that has no consciousness, a world of rocks and plants that change in connection with conscious beings who are trying to make sense of the connection. If you take away consciousness, you are left with nothing but change. There is an abyss between pure consciousness and pure mindlessness, a disconnect”.

Clint worked that out for himself during a seven-to-ten stretch for voluntary manslaughter. Thanks to Joseph Mazur’s marvellous book, I hope to be able to think with similar subtlety about matters temporal. Not now, you understand. But some time in the future …