“When you realize you are mortal,” the poet, painter, and philosopher Etel Adnan wrote while regarding a mountain, “you also realize the tremendousness of the future.” A decade earlier, shortly before a heart attack severed her lifetime, Hannah Arendt observed in her superb Gifford Lectures lectures on the life of the mind that our finitude, “set in an infinity of time stretching into both past and future, constitutes the infrastructure, as it were, of all mental activities.” While Arendt was composing these thoughts and silent cells were barricading one of her arteries, Ursula K. Le Guin was framing her novelistic inquiry into what it means to live responsibly, observing: “If time and reason are functions of each other, if we are creatures of time, then we had better know it, and try to make the best of it.” A generation before her, Borges had formulated the ultimate declaration of our temporal creatureliness, declaring: “Time is the substance I am made of. Time is a river which sweeps me along, but I am the river; it is a tiger which destroys me, but I am the tiger; it is a fire which consumes me, but I am the fire.”
Half a century of neuroscience and psychology have confirmed the physical fact beneath the poetic sentiment — we now know that our experience of Time is the crucible of empathy and the defining dimension of personal identity.

The young clerk at the Zurich patent office was thinking about none of this in the spring of 1905, the spring of a new century still verdant with possibility, when he dreamt up his general relativity — the refutation of Newton that would rattle the flow of existence, forever changing our understanding of Time; instead, Einstein was thinking of Time as a plaything of mathematics, the cold clay of an impartial universe in which we are playthings of chance.
After all, a revolution in understanding time is a revolution in understanding ourselves as creatures of Time. No human being — not even the most abstract-minded physicist — can think about Time without thinking about what it means to be human, to be concretely oneself, tender with transience.
That is the predicate of the slender, poetic 1993 novel Einstein’s Dreams (public library) by physicist Alan Lightman — a book about Time and the tricks we play on ourselves to bear our transience. This book does for Time what Alain de Botton’s The Course of Love does for love: punctuating a fictional world with philosophical quickenings, thought experiments, lyrical reflections on a fundamental human dimension of the real world.