“Whatever has happened, whatever is going to happen in the world, it is the living moment that contains the sum of the excitement, this moment in which we touch life and all the energy of the past and future,” Muriel Rukeyser wrote in one of the greatest books of all time.

“Fearlessness is what love seeks [which] exists only in the complete calm that can no longer be shaken by events expected of the future,” Hannah Arendt wrote in another of them, “hence the only valid tense is the present, the Now.”

But upon closer inspection, now — this elementary particle of eternity, this tiny and total locus of the living moment, this constant that is never the same — turns out to be more elusive than a neutrino, passing through us ghostly and ungraspable, yet leaving in its wake the purest sum of what we are.

Like love, now is an entirely subjective experience built on a meaningful interaction between systems. Like love, it is not a state but a process — a dynamic creation that enlists all of our past experience and the entire pattern of predictive perceptions we call reality. Like love, it is more like music than like mathematics.

Jo Marchant takes up this elemental mystery in her excellent investigation In Search of Now: The Science of the Present Moment (public library), weaving together physics, psychology, neuroscience, philosophy, and cultural anthropology to expose the warp and weft of our aliveness, locating in the living now “the origins of both life and mind, the driving force that powers behaviours, perceptions, choices and decisions, that ultimately carves out self and time.”

She writes:

It isn’t a location within time at all, but what makes time possible. Now is nature itself: the experienced, evolving universe within which all time, and all life, is held.

Two centuries after the vitalism debate sundered science into warring camps over the search for a “vital spark” that makes matter alive, we are finding that conscious minds — that crowning achievement of matter — are made of time and bodies undone by it, that it is the fundamental substrate of our aliveness. If the moment is the vital spark of time, the science of now — divisive, thrilling, inconclusive — is the vitalism debate of our time.

It began when Einstein defeated Bergson in their historic debate. Relativity rendered the flow of time, and the immediacy of the moment nested within it, not a given of physical reality but a function of the vantage you take. “The baggage of consciousness,” Einstein himself called our sense of time in a letter to his best friend. Like all radical ideas, relativity sent the ideological pendulum in the opposite direction and the ancients’ notion of eternalism — the idea that time is absolute, the same in all directions, and all existence simply is, without dynamic being that flows from past to present to future — was revived in the modern model of the block universe, configuring spacetime as an unchanging four-dimensional block. Marchant describes the implications of that model:

Our lives aren’t unfurling plots or stories; they are intricate paths already mapped out in four dimensions… Every cell within your body — your neurons, muscle cells, the blood cells pulsing through your arteries, capillaries and veins — has its own intricate, interconnecting life path carved out through the block. And not just every cell, but every atom. Each of us is made up of trillions of strands in space-time, all with their own complex trajectory. Your whole life might look like a sort of tree carved into the block, with disparate strands coming together at one end, representing your conception and birth; gradually thickening into a trunk; and then at the other end splaying out into finer and finer branches before disintegrating completely at the point of your death and decomposition… There is no room for movement, flow or happening. Reality doesn’t become. It just is.

If the physicists are right, our attachment to the specialness of the present moment is just another example of how our limited perception deceives us, like thinking the sky turns or the Earth is flat.

Causality, this model implies, is simply an interpretation based on our limited perception: “The flow from past to future… rather than being a fundamental feature of the universe… emerges as a secondary consequence of our inability to see the full picture.”

Then there is the predictive coding model, under which “what we perceive — the vibrant, changing, three-dimensional reality all around us — isn’t the external world at all, but a guided prediction, or as some have described it, a ‘controlled hallucination’… a prediction built from our history, both recent impressions and a lifetime of experience.”

It is worth remembering here that what gives science its loveliness and potency, and what distinguishes it from philosophy, is the passion for building models of how nature works calibrated by the rigor of testing them against reality. And yet time may be the only region where the models are truly and fundamentally untestable because the modeler is a captive of time. Einstein’s equations gave us the mathematical foundation for the Big Bang, but not even Einstein could travel back to the beginning of time to see if the model was true. This may be why, to me, the most compelling — as well as the most poetic — portion of Merchant’s investigation is the most empirical: an fMRI study that analyzed the patterns of brain activity in people watching a movie, which has a built-in timeline, or simply resting, capturing one image per second and comparing how these images — these portraits of the moment — differ from one another in order to render the experience of time’s passage. Marchant details the astonishing revelation:

There isn’t a simple progression from one brain state to the next as time passes, with each moment most similar to its nearest neighbour. Our “brain patterns are not simply counting off the seconds,” says [study author Dan] Lloyd. Hidden within the sequences was an organised temporal structure, with regular patterns in the way that subjects’ brains moved back and forth between a small number of states. In fact, the structure he found is very like that of music. Lloyd identified short, repeating motifs, or themes: sequences of states, between 4 and 11 seconds long, that look similar to each other. Often these themes recurred at constant time intervals: he called that “rhythm.” These rhythms appeared at a range of different timescales, and sometimes these frequencies were related to each other, so that they nested within one another perfectly. Lloyd called this structure “harmony” because it is analogous to the harmonic vibrations that give musical instruments, from violins to saxophones, their rich, resonant sound.

What this “harmony” means is that at any single moment, our spontaneous brain activity is made up of multiple, overlaid patterns and rhythms, which are related yet change over different timescales: just like our experience of Now. Each moment of neural activity is influenced by what’s happened in both the near and further past, and in turn influences what will happen in the near and further future. The results “suggest a human capacity to spread out from the immediate present tense of sensation, towards an overall temporal landscape,” Lloyd concludes. This explains how we can navigate fast-changing events yet at the same time hold on to stable threads of where we’re going and who we are.

An epoch before neuroimaging, Virginia Woolf intuited this truth when she considered the “moments of being” that make us who we are, intuited the musicality of being alive: “The whole world is a work of art [and] we are parts of the work of art,” she wrote in her breathtaking epiphany in the middle of the garden, “Hamlet or a Beethoven quartet is the truth about this vast mass that we call the world. But there is no Shakespeare, there is no Beethoven; certainly and emphatically there is no God; we are the words; we are the music; we are the thing itself.”

Looking through the kaleidoscope of the various models, Marchant considers the essence of the light:

It seems our perception of Now is a combination of two crucial factors: the ability to bind a hierarchy of different timescales together within each moment; and the inexorable progression from one moment to the next. This highly ordered temporal composition underpins our flowing stream of consciousness. Passing time is not just a characteristic we perceive: it is the underlying frame or structure through which we experience reality.

And yet it may be more important even than that, underpinning not just our world but who we are.

Our lives, Marchant argues, are only really alive, only ever real, as the moment lives itself through us:

The perceptions and sensations themselves — the call and response, the meeting or thwarting of predictions — these are reality. These are what existence is made of… Our perceptions or experiences — the melancholy of raindrops on a window, the exhilaration of diving into an icy pool — are real in themselves. There is no separate, enduring landscape beyond that they’re based on, no solid reference point against which our sensations can be judged.

[…]

Now has objective meaning as the expanding boundary at which reality is continually created. What’s coming into being includes not just the contents of the universe but its very structure. As new events occur, new universe — new space-time — is being born.

With an eye to all the different models of physics she examines in the book — relativity, the block universe, enactivism, and predictive coding among them — she ends where we ought to always begin: the discipline of not mistaking the model for the thing itself:

Do we exist as frozen snapshots or mathematical braids? Are we logic-bound computers or dynamic hurricanes? Are we living in a mental realm of shadows, separated from true reality by impenetrable, iron-like walls? Or are our perceptions real, while the familiar things of our world — even time and space themselves — are mere statistical structures, predictions that help us to manage our flow of sensations and stay alive?… Perhaps with all these possibilities there’s no way even to approach what lies beyond us, beyond our senses, beyond this point in time… All any of us can ever really know is that this moment exists. Maybe that’s enough. What we’re sensing and feeling, right here, right now, is real and undeniable, precisely because we are experiencing it.

Because there is no commons of now, the moment is the measure of our loneliness in time, but also the only region of space where we flower into being fully ourselves in a constant bloom of becoming.

Marchant writes:

What we perceive or experience in any moment is so personal, so utterly bound up in our individual history and biology, that it doesn’t make sense to speak of any “true,” definitive way of things outside that process… Our inner worlds — from feeling ownership of our bodies to experiencing emotions or recalling our life stories — are complex webs of probabilistic inferences, ever-changing depending on our circumstances, and recreated in each moment. There are no separate, enduring “selves” sitting behind… [We] exist as dynamic, living patterns of personal experiences, not stand-alone things. There’s no external stage on which we’re acting, no pre-existing terrain into which we’ve been parachuted. And, on the other side of the coin, there’s no pre-existing “us” either: no floating essences or souls ready to cast their gaze on the world.

This is not a negation of our being but an affirmation of it — a liberation from the tyranny and tedium of selfing we mistake for being:

What if instead of enduring entities — you and me, Earth and Sun — there are only the instants, the interactions? Only the burgeoning, interconnected, multilayered meshwork of creative sparks? From those sparks emerge selves and worlds — our private worlds of perception but also shared frameworks and structures: social, cultural, historical, scientific. Each instant, all of it is born and reborn.

[…]

Our experience of Now, I’m convinced, is not a hallucination. With every detail we choose to attend to, to breathe life into, we’re helping to write into existence both ourselves and the world… What if the universe wasn’t created in one Big Bang but, as Wheeler put it, “in billions upon billions of tiny creative flashes that are sounding out all around us”? This journey into Now has made me wonder whether reality might have given us not just one long-ago moment of creation but an ongoing miracle.

Now . . . Now . . . Now . . .

Perhaps, with our help, the whole universe is continually being made and remade. And the future isn’t written after all.