Well, I'm not so much asking about the true nature of change or movement but rather just what we mean to say when we say that something is changing or has changed. I take it that if I told any layperson that a block of wood changed from dark to pale when left out in the sun, they would understand what I mean by 'changed'. If interrogated as to the meaning of change they might say something like "well, it's when something is in one condition at one time, and the same thing is in another condition at another time. That's a change."
But obviously that's quite informal and ill suited to theoretical physics. On the other hand, physicists must have some basic idea of what a change or motion is. Yet I cannot think of anything more precise or firm than what I've said above.
If you go deep enough in physics, you don't have "wood". You just have a wavefunction. The wavefunction evolves with time in "classical" QM physics, and just exists statically in timeless physics.
And "the same thing" doesn't mean much, since there is nothing like "this electron" but only "one electron".
Saying that a piece of wood changed is an upper-level concept, which you can't directly define in fundamental physics, but only approximates (like "pressure", or "wood", or "liquid&q... (read more)