Time feels like the most basic feature of reality. Seconds tick, days pass, and everything from planetary motion to human memory seems to unfold along a single, irreversible direction. We are born and we die, in exactly that order. It feels so obvious that time moves forward that questioning it can seem almost pointless. Yet, for more than a century, physics has struggled to articulate what time actually is. This struggle is not philosophical nitpicking; it sits at the heart of some of the deepest problems in science.
Modern physics relies on different, but equally important, frameworks. One is Albert Einstein’s theory of general relativity, which describes the gravity and motion of large objects such as planets. Another is quantum mechanics, which governs the microcosmos of atoms and particles. And on an even larger scale, the standard model of cosmology describes the birth and evolution of the universe as a whole. All rely on time, yet they treat it in incompatible ways.
The Problem of Time in Modern Physics
When physicists try to combine these theories into a single framework, time often behaves in unexpected and troubling ways. Sometimes it stretches. Sometimes it slows. Sometimes it disappears entirely. Einstein’s theory of relativity was, in fact, the first major blow to our everyday intuition about time. Time, Einstein showed, is not universal. It runs at different speeds depending on gravity and motion. Two observers moving relative to one another will disagree about which events happened at the same time.
Quantum mechanics made things even stranger. In quantum theory, time is not something the theory explains. It is simply assumed. The equations of quantum mechanics describe how systems evolve with respect to time, but time itself remains an external parameter, a background clock that sits outside the theory. This mismatch becomes acute when physicists try to describe gravity at the quantum level, crucial for developing the much-coveted theory of everything. In many attempts to create such a theory, time vanishes as a parameter from the fundamental equations altogether. The universe appears frozen, described by equations that make no reference to change.
The puzzle of time remains one of the most persistent obstacles to a unified theory of physics. Despite enormous progress in cosmology and particle physics, we still lack a clear explanation for why time flows at all.
Entropy and the Arrow of Time
When physicists try to explain the direction of time, they often turn to a concept called entropy. The second law of thermodynamics states that disorder tends to increase. A glass can fall and shatter into a mess, but the shards never spontaneously leap back together. This asymmetry between past and future is often identified with the arrow of time.
This idea has been enormously influential. It explains why many processes are irreversible, including why we remember the past but not the future. If the universe started in a state of low entropy and is getting messier as it evolves, that appears to explain why time moves forward. But entropy does not fully solve the problem of time. The fundamental quantum mechanical equations of physics do not distinguish between past and future. The arrow of time emerges only when we consider large numbers of particles and statistical behavior.
The Information Revolution in Physics
Over the past few decades, a quiet but far-reaching revolution has taken place in physics. Information, once treated as an abstract bookkeeping tool used to track states or probabilities, has increasingly been recognized as a physical quantity in its own right, just like matter or radiation. While entropy measures how many microscopic states are possible, information measures how physical interactions limit and record those possibilities.
This shift did not happen overnight. It emerged gradually, driven by puzzles at the intersection of thermodynamics, quantum mechanics, and gravity, where treating information as merely mathematical began to produce contradictions. One of the earliest cracks appeared in black hole physics. When Stephen Hawking showed that black holes emit thermal radiation, it raised a disturbing possibility: information about whatever falls into a black hole might be permanently lost as heat. That conclusion conflicted with quantum mechanics, which demands that the entirety of information be preserved.
Resolving this tension forced physicists to confront a deeper truth. Information is not optional. If we want a full description of the universe that includes quantum mechanics, information cannot simply disappear without undermining the foundations of physics.
Emergent Gravity and Information
In parallel, surprising connections emerged between gravity and thermodynamics. It was shown that Einstein’s equations can be derived from thermodynamic principles that link spacetime geometry directly to entropy and information. In this view, gravity doesn’t behave exactly like a fundamental force. Instead, gravity appears to be what physicists call “emergent”—a phenomenon describing something that’s greater than the sum of its parts, arising from more fundamental constituents.
Similarly, gravity can be described as an emergent phenomenon, arising from statistical processes. Some physicists have even suggested that gravity itself may emerge from information, reflecting how information is distributed, encoded, and processed. These ideas invite a radical shift in perspective. Instead of treating spacetime as primary, and information as something that lives inside it, information may be the more fundamental ingredient from which spacetime itself emerges.
A Recording Cosmos and the Nature of Time
This has an important implication. If spacetime records information, then its present state reflects not only what exists now, but everything that has happened before. Regions that have experienced more interactions carry a different imprint of information than regions that have experienced fewer. The universe, in this view, does not merely evolve according to timeless laws applied to changing states. It remembers.
This memory is not metaphorical. Every physical interaction leaves an informational trace. Although the basic equations of quantum mechanics can be run forwards or backwards in time, real interactions never happen in isolation. They inevitably involve surroundings, leak information outward, and leave lasting records of what has occurred. Once this information has spread into the wider environment, recovering it would require undoing not just a single event, but every physical change it caused along the way. In practice, that is impossible.
This is why information cannot be erased and broken cups do not reassemble. But the implication runs deeper. Each interaction writes something permanent into the structure of the universe, whether at the scale of atoms colliding or galaxies forming.
Time Arising from Information
Recently, researchers extended this informational perspective to time itself. Rather than treating time as a fundamental background parameter, they showed that temporal order emerges from irreversible information imprinting. In this view, time is not something added to physics by hand. It arises because information is written in physical processes and, under the known laws of thermodynamics and quantum physics, cannot be globally unwritten again.
Every interaction, such as two particles crashing, writes information into the universe. These imprints accumulate. Because they cannot be erased, they define a natural ordering of events. Earlier states are those with fewer informational records. Later states are those with more. Quantum equations do not prefer a direction of time, but the process of information spreading does. Once information has been spread out, there is no physical path back to a state in which it was localized. Temporal order is therefore anchored in this irreversibility, not in the equations themselves.
The future differs from the past because the universe contains more information about the past than it ever can about the future. This explains why time has a direction without relying on special, low-entropy initial conditions or purely statistical arguments.
Testing the Theory of Informational Time
But could we ever test this theory? Ideas about time are often accused of being philosophical rather than scientific. Because time is so deeply woven into how we describe change, it is easy to assume that any attempt to rethink it must remain abstract. An informational approach, however, makes concrete predictions and connects directly to systems we can observe, model, and in some cases experimentally probe.
Black holes provide a natural testing ground, as they seem to suggest information is erased. In the informational framework, this conflict is resolved by recognizing that information is not destroyed but imprinted into spacetime before crossing the horizon. The black hole records it. As the black hole evaporates through Hawking radiation, the accumulated informational record does not vanish. Instead, it affects how radiation is emitted. The radiation should carry subtle signs that reflect the black hole’s history.
The same principles can be explored in much smaller, controlled systems. In laboratory experiments with quantum computers, qubits (the quantum computer equivalent of bits) can be treated as finite-capacity information cells, just like the spacetime ones. Researchers have shown that even when the underlying quantum equations are reversible, the way information is written, spread, and retrieved can generate an effective arrow of time in the lab.
These experiments allow physicists to test how information storage limits affect reversibility, without needing cosmological or astrophysical systems.
What Time Really Is
Ideas about information do not replace relativity or quantum mechanics. In everyday conditions, informational time closely tracks the time measured by clocks. For most practical purposes, the familiar picture of time works extremely well. The difference appears in regimes where conventional descriptions struggle.
Near black hole horizons or during the earliest moments of the universe, the usual notion of time as a smooth, external coordinate becomes ambiguous. Informational time, by contrast, remains well defined as long as interactions occur and information is irreversibly recorded.
This shift reframes the longstanding debate. The question is no longer whether time must be assumed as a fundamental ingredient of the universe, but whether it reflects a deeper underlying process. In this view, the arrow of time can emerge naturally from physical interactions that record information and cannot be undone. Time, then, is not a mysterious background parameter standing apart from physics. It is something the universe generates internally through its own dynamics. It is not ultimately a fundamental part of reality, but emerges from more basic constituents such as information.
Whether this framework turns out to be a final answer or a stepping stone remains to be seen. Like many ideas in fundamental physics, it will stand or fall based on how well it connects theory to observation. But it already suggests a striking change in perspective. The universe does not simply exist in time. Time is something the universe continuously writes into itself.
