Time is not a coordinate. But that doesn't mean time isn't real. For instance it seems inconvenient to formulate what an algorithm is in "timeless" semantics for physics. Scott Aaronson has a relevant essay about this here. Maybe to a lesser extent it seem inconvenient to talk about entropy.
Has anyone read "Time's arrow and Archimedes's point"?
When I was originally exposed to this idea it was through Buddhism and it disturbed the hell out of me (or should I say disrupted?). I think it was the first time I'd have a significant internal assumption / logic challenged and it set off one of my first runs of exploring "what else isn't fundamentally sound?".
Originally I had this presented by trying to prove both elements (time, and change) then trying to prove the relationship between the two. To simplify and kludge the demonstration - I can push a cup onto the floor and it breaks. It's a sequence of change that at least I can observe in a fairly common way to unfold right in front of me and have a few fairly dependable priors (gravity, physical interaction, etc) to leverage to explain it.
Meanwhile time, without the assistance of a short-frequency-repetitive-change-device (a watch) is as far as I can tell literally impossible to assemble using the basic concepts and objects around me. I can reliably demonstrate that as long as a watch has power it will continue to drive the hands forward on a series of different increments, but I can't relate that back to "time" in a consistent way. Nor does the breaking of the cup demonstrate time effectively.
Going the other way and coming back, I find it beyond my reasoning to equate time as a function of change, or change having a dependency on time. I can certainly demonstrate all kinds of change (and perceived cycles of change such as daytime and night time), but I can't demonstrate time at all without overlapping the observation / fundamentals of a series of changes.
There's still a lot of inconsistencies but examining the series of events and changes that drove me to this current moment and then the series of actions that will come from events happening now, I'd be more confident saying that the universe is a perpetually incremental state machine rather than it has some internal or reliable additional component of time that is causing it to all occur. Zen texts explore this concept in terms of wood that burns to form ash and then mixes with water to form silt. Time isn't considered, the events are viewed as timeless, it's the change of state that is the significant "measure".
Today's post, Timeless Physics was originally published on 27 May 2008. A summary (taken from the LW wiki):
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