I haven't read Rovelli's pop-sci book. Could you glance through the table of contents and/or the index and look for, among other things, "thermal time" and "time emerges in a world without time"? I would be astonished if he did not discuss these ideas at length in his book.

> Rovelli's words from a book 23 years newer than your referenced article, seem to directly contradict what you're arguing

Ok, let's deal with that. It's not like he stopped writing on the topic or substantially changed his position (rather than elucidating it).

You can click on arXiv:1505.01125, arXiv:1407.3384, and arXiV:0903.3832 in the search below; each paper directly supports what I wrote. The first two digits of any arXiv ref is the year of submission.

https://arxiv.org/search/advanced?advanced=&terms-0-operator...

Or alternatively you can take this approach, following his self-citations of Connes & Rovelli 1994:

https://scholar.google.com/scholar?hl=en&as_sdt=2005&sciodt=...

however not all of those are directly relevant to this particular argument.

> he explicitly states he does not believe we live in a block universe

Can you extract from the book the couple paragraphs around where he says that explicitly? I bet it'll be easy to clarify. I'll even take a preemptive guess.

We'll have to digress briefly into (hopefully scientific) philosophy.

The (eternalist) block universe point of view is essentially that the universe is deterministic: if you have the full details of the state of the universe at a particular time, you have the full details of the state of the universe at every other time too. This is fundamental to the https://en.wikipedia.org/wiki/Initial_value_formulation_(gen... about which Rovelli has written extensively (e.g. at https://arxiv.org/abs/gr-qc/0202079 and chapter 4 of his book Quantum Gravity, draft on his own page http://www.cpt.univ-mrs.fr/~rovelli/book.pdf ).

Unfortunately philosophers have several different versions of "block universe" with varying degrees of determinism. The growing block universe, for instance, holds that the past exists, that the present is an objective quantity, and that the future does not yet exist (as in it is not fully determined) at the the present of the growing block. Is it possible that Rovelli was rightly criticizing that, and you or he or his editor missed a "growing" in "growing block universe"?

Returning to his Quantum Gravity book, I'm happy to recommend §2.4 generally, although it is far from pop-sci. In 2.4.4 (p 58, pdf page 76) he distinguishes ten different notions of time. Clearly not all of these can be equally fundamental; his argument is that none of them is fundamental in that they are demanded by all possible theories compatible with General Relativity in its classical limit. However, as some of the ten are directly measurable, one cannot (and he does not) argue they they do not exist -- rather they emerge from correlations between observables.

Now we can leave the philosophical.

The scientific content of his Quantum Gravity book's central conjectures are that not only is it feasible to write down physical behaviours without recourse to time as a fundamental quantity, those behaviours' descriptions take an especially simple form when one does so in the way he proposes through the course of the book. The first of these points is not really scientifically controversial.

> No, I am saying specifically that saying something is happening /now/ when it is outside of our light cone is a meaningless statement.

There is no single correct definition of now in a general curved spacetime; there is instead a democracy of "now"s. Each microscopic portion of your body has its own separate causal cone, and at any particular instant the ones on microscopic things near your scalp are spacelike separated from the ones near the soles of your feet. Does that make stubbing your toe meaningless?

> "The present is a localized rather than a global phenomenon"

It's an idiosyncracy rather than a phenomenon at all. By the time you have perceptual awareness of your toe-stub it is ancient history on the scale of electron interactions between your skin and the leg of the table or whatever, and indeed the daughter products of the scatterings (there will be at least some photons and gravitational waves shed) will have raced past your brain to as far as outside the orbit of the moon. You have free choice of "nows", and no fundamental reason to choose which of them to apply.

> localized

From a purely technical perspective, we can always apply Fermi coordinates to anything freely falling in a Lorentzian spacetime (as ours is, to the best of our ability to test directly or via astrophysical observation). This guarantees a minimum definition of "local". However, the coordinates are peculiar to the object; although we can certainly extend Fermi coordinates into a https://en.wikipedia.org/wiki/Local_reference_frame?oldforma... , frames of reference do not determine the physical behaviours. As you and I drift past each other in deep space, there are only personal reasons to choose a set of Cartesian coordinates with you at the origin over a set of Spherical coordinates with me at the origin.

If we drift past each other with high enough relative velocity, then even when we are extremely close to each other -- much closer than the scale of the earth -- your wristwatch now and my wristwatch now will not generally agree. (Assuming they are identically constructed, if they agree at some instant, they will disagree at other instants). This is true even if at all relevant times we are well within each other's causal cones.

So some ideas of "now" fail at scales much smaller than that of Earth's radius.

Others might survive at scales much larger: we've been doing Einstein-synchronization experiments since the Viking missions to Mars, and we can straightforwardly predict https://en.wikipedia.org/wiki/Barycentric_Dynamical_Time anywhere in the solar system. So we can say at time X TDB Mars-based spaceprobe should activate instrument Y. Although it might take us a couple minutes to verify that spaceprobe activated Y at X, we can be pretty confident before those two minutes expire as our TDB clock registered X, its TDB clock also registered X.

Likewise, we can synchronize in principle with a distant observer of the Cosmic Microwave Background such that we each agree to do something when the CMB's dipole-free spectrum is closest to a blackbody of X kelvins. Assuming honesty, we can be pretty confident that millions of years later we will see that their "CMB clock" registered X kelvins when they began the agreed action.

These are among the infinite supply of idiosyncratic "now"s that can be useful even if they are in no way fundamental. Utility surely implies meaningfulness, even if neither utility nor meaningfulness implies universality.

> As for what I believe, I'm not sure.

Good. Neither am I. Neither is Rovelli, if he is honest. There is a lot of room to research the various problems of time.

> I don't understand [...] why Rovelli's non-science paper writings seem to argue very differently than what you are saying.

As I said, I don't know what the non-science papers say exactly; if you feel like pasting extracts in reply, we can try to sort this out. Any of your guesses in your final paragraph could be right, or it could be something else.