The Order of Time

This book introduces time as a profound mystery, deeply intertwined with the mind and universe. While our human perception experiences time as familiar and uniform, scientific discoveries reveal a fundamentally different, non-linear structure. The text embarks on a journey to dismantle our common understanding, explaining how time does not exist in a fundamental sense but emerges from our perspective.

Time is not uniform; it runs faster in mountains than at sea level due to gravity, as predicted by Einstein. This means there is no single, universal time or shared "present" for the entire universe. Instead, every point in space and every moving object has its own distinct rhythm, leading to a multitude of proper times and a distorted temporal structure.

Most fundamental laws of physics are time-symmetric, meaning they don't distinguish past from future. The only exception is the law of entropy, which states heat moves from hot to cold. This increasing disorder creates the "arrow of time," though it's viewed as a result of our blurred vision of microscopic reality rather than an intrinsic universal property.

Historically, the debate between Aristotle's view of time as a measure of change and Newton's absolute time was resolved by Einstein. He demonstrated that spacetime is actually the gravitational field itself. This means time is not an independent container but a dynamic physical entity, capable of being warped and influenced by matter, acting like an elastic sheet.

At a microscopic level, universal time disintegrates into fluctuating proper times. Quantum gravity, particularly loop quantum gravity, reveals time to be granular, with a minimum Planck interval. Indeterminacy blurs the past, present, and future, as spacetime fluctuates. Ultimately, time emerges as a fragmented network of relations rather than a coherent underlying canvas.

Without a fundamental time variable, the world is better understood as a collection of events, not permanent things. Even seemingly solid objects are long-duration events or complex vibrations. This perspective emphasizes "becoming" over "being," portraying the universe as a network of happenings rather than a container for static substances.

Physics can describe the world without an external time variable by focusing on how variables change in relation to one another. Equations like the Wheeler-DeWitt equation describe possible events and their correlations. In loop quantum gravity, space and time emerge from the interaction of elementary quanta within spin networks and spinfoams, rather than acting as a fixed background.

The human experience of time is an emergent phenomenon, akin to "high" and "low" on a planet. It arises from ignorance of microscopic details, where our macroscopic state defines thermal time. This blurring, combined with quantum noncommutativity, creates the flow of time, fundamentally linking our perception to what we overlook in the universe.

The arrow of time and the growth of entropy are presented as effects of perspective, not intrinsic universal laws. Our situatedness within the world, observing it from the inside through limited variables, influences our perception. For small systems, entropy appears high due to indistinguishable microscopic details, creating the perceived flow of time.

Human identity is a collection of relations and events, defined by a localized point of view, the brain's grouping tendencies, and memory. Memory is crucial, linking past to present and allowing the brain to predict the future. Our internal perception of time is sustained by these traces and anticipations, even as fundamental physics suggests no objective, universal flow.

The book addresses the philosophical debate on time's reality, arguing against the idea that time is an illusion simply due to the absence of a global present. It critiques inflexible definitions of time and ontological interpretations of Einstein's simultaneity. Instead, it suggests that time's properties emerge from a system's statistical state and the blurring inherent in our interaction with the world.