>>12174803No, we don't know.
So far there has been no "time particle" or field, no time force and no absolute time unit.
With time being relative and getting faster in high gravity regions, we can assume it is linked to the movement of particles, which leads us to entropy.
So if we stop particles from moving, as in we stop entropy from increasing, by say cooling the universe to 0 K (which is impossible anyway) we might have stopped time itself - this of course being a play of definitions and saying time is (a consequence of) entropy - this assumes that our universe is a closed system.
It might not be anything "real" at all, just a consequence we experience due to entropy. Asking why time "moves" in the first place might just be a question we are not able to answer ever, just like you cannot decompile a program within an instance of it without access to the "outside", which is getting close to theistic interpretations.
Gravity is similar in some aspects, maybe there is a mediating particle, a graviton, though there is nothing really that hints at this, gravity might just be a consequence of spacetime curvature over time.
