How a Timeless World Gains a Past and a Future ⚡ экспресс
Quantum gravity describes a universe without fundamental time, which creates paradoxes. One of them is the 'cosine problem': when calculating transition probabilities in path integrals, the amplitudes include both forward and backward in time contributions, contradicting our experience of unidirectional time. The authors showed that if we single out a 'clock' subsystem and put it into a semiclassical state, it establishes an arrow of time, automatically selecting only the forward contribution. Thus time emerges as an emergent property without altering fundamental laws.
The deepest equations of physics, like the Wheeler–DeWitt 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.
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.