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How a Timeless World Gains a Past and a Future ⚡ экспресс

Original: "The problem of time: a path integral view"
· Juan Manuel Diaz, Alejandro Perez
arXiv:2605.17935 · 2026-05-18 · CC BY · ⏱ 1 min · General Relativity HEP Theory Quantum Physics
Physicists have shown that the arrow of time is not baked into the laws of nature but emerges as soon as you identify a ‘clock’ within the Universe itself.
Abstract

In quantum physics, time may not be fundamental, but rather emerge from a deeper timeless reality — like frames in a movie, all existing at once yet creating the illusion of motion when played. Scientists have shown that if a system contains a 'clock' (like a moving particle) that behaves classically, the familiar flow of time appears. What if the entire Universe is such a movie without a projector?

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The deepest equations of physics, like the WheelerDeWitt equation, contain no time. Past and future are scrambled within them, like frames on a film reel with no arrow indicating which way to play it. This symmetry is not a flaw but a feature.

By summing over all possible histories, the theory yields an equal mixture of forward and backward evolutions—this is known as the cosine problem. But as soon as you single out a ‘clock’ inside the universe—any subsystem that sets a rhythm—the symmetry breaks. The clock becomes a projector: the sum of histories now prefers one direction.

Thus, in quantum gravity (for instance, in the work of Rovelli), the flow of time is born spontaneously. No tweaking of the laws: an internal metronome turns chaos into the arrow of time. This also explains how time could have started after the Big Bang. And most astonishingly, any sufficiently large object—even a spinning galaxy—can act as such a clock, selecting a future from a fan of possibilities.

🎯 Paradox: time doesn’t flow on its own—it requires an ‘observer’ in the form of a physical clock. Without one, all moments exist at once, like frames on a frozen film reel.

🎬 Just like in ‘Tenet’, where reversed entropy turns time backward, the new work shows that at a fundamental level, motion in either direction is equally valid—until a clock intervenes.

\exp(iS/\hbar)+\exp(-iS/\hbar)
sum of two quantum trajectories—one toward the future and one toward the past; S is the accumulated action, ħ is Planck’s constant
Scientists
Alan GuthAndrei LindeGeorges LemaîtreJames PeeblesAdam RiessBrian Schmidt
Tags
entropy spacetime curvature big bang
Laws
Friedmann equationsHubble's lawsecond law of thermodynamicsBekenstein-Hawking entropyEinstein field equationsPlanck's law
Original: arXiv:2605.17935 · CC BY · bridge42worlds