The core idea of relational quantum mechanics is that when we talk about an object — be it an atom, a person or a galaxy — we are never just referring to the system alone. Rather, we are always referring to the interactions between this system and something else. We can only describe — and in fact understand — a thing as it relates to ourselves, or to our measuring devices.
Lee Smolin has gone down a different track but with similar spirit of sorts. Carlo poked fun at Lee for all the work they've done together despite disagreeing on so much in his recent talk[1] at Lee's Fest[2].
Smolin has named his approach the Causal Theory of Views, in which he postulates that spacetime emerges from events, ie relational interactions. This[3] interview, which is a few years old now, contains a decent high-level explanation. The idea that kinda overlaps with Rovelli he explains like this:
The theory that I've been looking for would take advantage of the fact that the notion of locality and nonlocality is key to understanding quantum mechanics, and then try to understand that with the lens of the unification of quantum physics with space and time, which is quantum gravity.
In both approaches, there's a principle, which is the idea of relational physics—that the degrees of freedom, the properties of whatever it is that's dynamical that you're studying, arises from dynamical relationships with other degrees of freedom.
In other words, you don't have absolute space, you don't have particles that occupy points or follow paths or trajectories in absolute space. You have many particles which, between them, allow you to define relative motion.
Lee has given several talks[4] at PIRSA since that interview with more details as he's developed his idea.
So while both go hard on the relational aspect, they disagree on some fundamental things. Rovelli thinks time is an illusion, but in Lee's CTV time is real and space is the illusion (emergent).
Who knows if it'll pan out or be a dead end, but since the quantum physics community has been headbutting the fundamental issues with little progress for so many decades, it seems prudent to try some bold approaches.
[1]: https://pirsa.org/25060030
[3]: https://www.edge.org/conversation/lee_smolin-the-causal-theo...
I'm not a physicist by any means but I was just thinking something similar only a few minutes ago... that humans (or anything) ageing probably only exists as a function of the passage of time, but if all matter stopped moving, even in an isolated area, there is seemingly no longer a passage of time there. So maybe time itself only exists insofar as our ability to measure relative changes to matter.
A crazy thought I had in my sleep: What if dark matter only exists as a random noise generator to keep the simulation from halting? /s
My brain is weird.
> but if all matter stopped moving, even in an isolated area, there is seemingly no longer a passage of time there
This is kinda what would happen in Penrose's Conformal Cyclic Cosmology[1], as far as I can gather. In his theory, he posits that in the far future, matter has decayed to radiation, and energy has been redshifted into infinity thanks to the expansion of space.
As such, in a local region things would seemingly be frozen in time. Nothing would change, entropy would not increase, and hence no apparent passing of time.
That said, his theory is pretty speculative. But fun to think about.
[1]: https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology