I'd still like to know what either "flows" or "chunks".
Time? Sure, ok, time flows, or time chunks. But what exactly is it?
Time has been one of my favorite topics to read about in the last 20 or so years, and I still feel like we have hardly made any progress in figuring it out.
It may be (probably is) that "what is this" or "why does it do that" are just meaningless questions, in the sense a child (or adult who hasn't re-calibrated their expectations of what science can tell them) means them. Which is interesting itself, I suppose, but at that point just go study philosophy and art, if that's why you were into science in the first place—and I think it's why everyone at least begins to be interested in science.
[EDIT] in particular it's frightening how fast kids' questions stymie an adult because the adult realizes that they're only a step or two away from "why is there something instead of nothing, and also what is something?" and... good lord, at that point seriously just go become religious or get really into philosophy or something, because you're outta luck, kid, sorry, we don't have any actual answers, just observations about what all this stuff does, but no we can't tell you what "stuff" or "does" are.
He also points out that, ever since Newton, the dream of mechanistic world was shattered, and with it, any hope that science would help us "make sense of the world" in a truly satisfying sense. Instead, we have become content with modelling the world mathematically and predicting how it will evolve.
Of course, space-time and quantum mechanics have driven additional nails in the coffin of a truly understandable world.
I'd think the opposite. The fact the world can work at least as strangely as relativity and quantum mechanics suggest, and we still figured those out as much as we have so far, reassures me in our ability to figure out the world we exist in.
However, we can still hope to model and predict it more accurately than we would have ever hoped before, so there is that :)
I myself lean to the Aristotelian definition: count of change.
After all, all our clocks are built on this definition. If there were a lone particle traveling in an infinite universe, it'd be nonsensical to talk about its speed because there'd be nothing to relate the distance traveled to (and no observer). Indeed, whenever we talk about "time" and related quantities like "speed", we always compare the observed object to some other, existing reference.
So I think of the interaction of particles/matter as being something fundamental, whereas "time" is a synthetic human notion.
Except! There would still be virtual particles creating and annihilating. Let's assume that there is an interval between these events (e.g., they aren't constantly present).
Would Aristotle say that no time passes between events? I would tend to say that time yet passes even during the periods when nothing else exists and nothing is happening.
Let's say the second to last things in the universe were another observer with a clock who could time and observe these virtual particle events, and this observer was able to time these events at a 1 second interval between events (duration of event is irrelevant).
And then that second-to-last observer and the clock suddenly annihilate somehow so that only your immutable particle remains. And the virtual particle events still happen at the same interval period.
Would the time interval between virtual particle events somehow be different without the clock/observer as with the sole immutable particle? That doesn't make sense to me, though I will certainly admit that it could very well be!
Aristotle's idea of time is not fully satisfactory to me, though I can't of course rule it out.
[0] Important! Because if the particle is not immutable, then it is waiting for change, which requires time.
So, if this is true, then does it mean that time does not 'flow', but rather 'chunks'?
(even at the macro level, a river that moves a specified number of molecules per time unit doesn't "flow", it's technically moving discrete "chunks" of water, we just don't say it's moving chunks of water because no one cares about the "well, technically..." in normal conversation. We know what's meant and what to ignore. Physics doesn't have that luxury)
We have no idea where that boundary can even be found; it would certainly have to be below the Planck length, but we have nothing that allows for that kind of precision. The only thing physics can say right now, and possible even ever can, is that nothing we have at our disposal allows us to conclude time "actually is" discrete. We can come up with mathematical frameworks that assume time is a discrete dimension, but even if those yield super accurate predictions that are then verified through experiment, all that does is confirm that a continuous dimension can be reduced to a discrete one without loss of precision.
“Time is what the clock measures.”
Carroll, From Eternity to Here - reasonably good and quite accessible.
Coveney, The Arrow of Time - better than average
All of my books are packed away right now for a move, so I'm sorry I can't come up with more. Though that Carroll book is really a decent entry point.