A growing body of theoretical and experimental work in physics is converging on a striking possibility: time, the dimension humans experience as a constant forward flow, may not be a fundamental feature of reality at all. Researchers working across quantum gravity, quantum information theory, and thermodynamics have spent decades building mathematical frameworks in which time dissolves into something secondary, an artifact of deeper physical processes. That quiet effort has gained fresh momentum, with new papers and review articles in early 2026, including a survey of time arising from information, pulling these threads together and pushing the question from abstract theory toward testable science.
The Wheeler-DeWitt Problem: Where Time Disappears
The tension starts with a well-known clash between the two pillars of modern physics. General relativity treats time as flexible, woven into the geometry of spacetime, while quantum mechanics treats it as a fixed background parameter, ticking uniformly while particles evolve. When theorists try to merge the two into a single quantum theory of gravity, time drops out of the equations entirely. Bryce DeWitt’s canonical quantization of general relativity, published in Physical Review, produced constraint equations with no ordinary time evolution, a result now central to the Wheeler-DeWitt framework. The universe, described by these equations, simply exists in a static quantum state with no built-in clock, leaving no obvious place for the familiar notion of a moment-to-moment history.
Physicists call this the “problem of time,” and it has shaped decades of research. C. J. Isham catalogued the difficulty in a chapter for the proceedings of the 117th WE Heraeus Seminar held in September 1993, classifying the many proposed resolutions and showing how deeply the issue runs through canonical quantum gravity. Robert M. Wald separately outlined an approach to defining states and local observables without a fundamental time variable, framing what any genuine solution would need to accomplish. In that work, time at the Planck scale is not assumed to exist as an external parameter at all, and observable evolution can be described using only correlations among fields. The message from these independent lines of inquiry is consistent: the deepest layer of physics may have no room for time as we ordinarily conceive it, even though effective notions of time reappear at larger scales.
How Clocks Create the Illusion of Change
If the universe is fundamentally timeless, where does the vivid experience of seconds passing come from? One influential answer traces back to Don Page and William Wootters, whose mechanism, published in Physical Review D, showed that a globally stationary quantum state of a closed system can still produce effective dynamics. Their idea is to split the universe into a “clock” subsystem and the rest. Although the total quantum state does not evolve in any external time, subsystems become entangled so that different clock readings are correlated with different states of the rest of the universe. An observer who uses the internal clock to label events experiences change, even though nothing evolves relative to an outside parameter. Time, in this view, is not a stage on which events unfold but a relational property emerging from correlations within a timeless whole.
That proposal moved from pure theory to the laboratory when researchers used entangled photons to illustrate the Page–Wootters picture. Their experiment, reported in Physical Review A, explicitly contrasted what an internal observer measuring correlations with the clock subsystem would see against what an external observer, looking at the full entangled state, would record. The internal observer detected ordinary quantum evolution: the “system” photon appeared to change as the “clock” photon advanced. The external observer, by contrast, saw a static, time-independent global state. Both descriptions were valid simultaneously, separated only by perspective. Analyses in venues such as The Conversation have linked this relational view to the block-universe picture already implicit in relativity, where all events coexist in a four-dimensional structure and the flow of time is not an objective feature but a way certain observers trace paths through that structure.
Thermal Time: Temperature as the Speed of the Clock
A separate but compatible line of reasoning ties the emergence of time to thermodynamics rather than to quantum correlations alone. Alain Connes and Carlo Rovelli formulated the thermal time hypothesis, proposing that physical time flow in generally covariant quantum theories is state-dependent and derived from the thermodynamical state using Tomita–Takesaki theory, a sophisticated tool from algebraic quantum field theory. In accessible terms, the direction and rate of time are not baked into the fundamental equations but arise from the statistical properties of whatever state the universe, or a subsystem of it, happens to occupy. The usual time parameter of quantum mechanics is replaced by a “thermal” parameter generated by the modular structure of the state, making time an emergent bookkeeping device for change in systems out of equilibrium.
Rovelli and Matteo Smerlak later applied thermal time ideas to stationary spacetimes and connected them to the Tolman–Ehrenfest relation, a known result in general relativity linking temperature gradients to gravitational fields. Their work recast local temperature as a kind of speed of time, grounding the abstract framework in concrete physics by showing that hotter regions effectively run through thermal time at a different rate than colder ones. If the thermal time hypothesis is correct, clocks tick at different rates not just because of relativistic effects on spacetime but because the local thermodynamic state literally helps define what “time” means in that region. This approach does more than reinterpret equations: by tying emergent time to measurable thermal phenomena, it offers a route toward empirical scrutiny that purely formal arguments about timeless wavefunctions cannot easily provide.
New Theories Push the Boundaries Further
Recent proposals have gone beyond removing time from the foundations and started rebuilding physics with time in unfamiliar roles. One such model, developed by a researcher at the University of Alaska Fairbanks, inverts the usual priority of space and time by treating time as the single fundamental property in which all physical phenomena occur, while spatial dimensions are secondary, emergent features. A report on this work describes a framework in which matter, fields, and even the geometry of space arise from patterns in a one-dimensional temporal substrate, aligning with broader suggestions that space may be a secondary effect of deeper time-based structure. Instead of quantizing spacetime, the theory starts from pure time and derives spatial relations as effective descriptions of how processes unfold within that fundamental temporal order.
Placed alongside the Wheeler–DeWitt framework, the Page–Wootters mechanism, and the thermal time hypothesis, this kind of time-first approach underscores how fluid the concept of time has become in cutting-edge physics. Some programs argue that time disappears at the deepest level and returns only as an emergent parameter tied to entanglement or thermodynamics; others suggest that time is the only primitive ingredient and that space, and perhaps gravity, are emergent. The common thread is that neither everyday time nor everyday space can be taken for granted. Instead, they appear as effective, approximate structures arising from more abstract, often information-theoretic substrates.
From Philosophy to Testable Physics
For much of the twentieth century, debates about whether time is real or illusory were relegated to philosophy, even when they drew inspiration from relativity and quantum mechanics. The situation is changing as researchers translate these ideas into concrete models and experimental proposals. The entangled-photon implementation of the Page–Wootters mechanism shows how relational time can be probed in the lab, while thermal time connects the arrow and rate of time to measurable temperature distributions in gravitational fields. At the same time, information-based approaches argue that what we perceive as temporal order may be rooted in the way observers compress and process data, an idea emphasized in recent discussions of time emerging from information rather than from an external cosmic clock.
These developments do not yet amount to a single, unified picture of time, and many open questions remain. Can a fully timeless formulation of quantum gravity recover all observed relativistic effects without reintroducing a hidden time parameter? Will thermal time or related ideas yield unambiguous predictions that distinguish them from standard quantum field theory in curved spacetime? And if space is emergent from a more fundamental temporal or informational structure, what new phenomena should appear at the smallest scales or highest energies? As theorists refine their models and experimentalists devise clever tests, the familiar intuition of time as an ever-advancing river looks increasingly like an approximation to something stranger and more subtle. Whether time ultimately proves to be fundamental, emergent, or illusory, the effort to pin it down is reshaping our understanding of reality at its most basic level.
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*This article was researched with the help of AI, with human editors creating the final content.
