Back on my feet, I ran into Proust in another unexpected place. How he would've loved this:
It is not reality that has a time flow, but our very approximate knowledge of reality. Time is the effect of our ignorance.That stunning lyric is spoken by "Carlo Rovelli, a physicist at the University of Marseille in France," who has been working to demonstrate that time is "an illusion," according to this article, or perhaps more accurately, a statistical generalization:
For more than a decade, he has been working with mathematician Alain Connes at the College de France in Paris to understand how a time-free reality could give rise to the appearance of time. Their idea, called the thermal time hypothesis, suggests that time emerges as a statistical effect, in the same way that temperature emerges from averaging the behaviour of large groups of molecules (Classical and Quantum Gravity, vol 11, p 2899).That would be a wonderful final exam: "write three pages of In Search of Lost Time in which Proust expounds upon the ideas in this New Scientist article."
Imagine gas in a box. In principle we could keep track of the position and momentum of each molecule at every instant and have total knowledge of the microscopic state of our surroundings. In this scenario, no such thing as temperature exists; instead we have an ever-changing arrangement of molecules. Keeping track of all that information is not feasible in practice, but we can average the microscopic behaviour to derive a macroscopic description. We condense all the information about the momenta of the molecules into a single measure, an average that we call temperature.
According to Connes and Rovelli, the same applies to the universe at large. There are many more constituents to keep track of: not only do we have particles of matter to deal with, we also have space itself and therefore gravity. When we average over this vast microscopic arrangement, the macroscopic feature that emerges is not temperature, but time. "It is not reality that has a time flow, it is our very approximate knowledge of reality that has a time flow," says Rovelli. "Time is the effect of our ignorance."