[Physics] Physics Digest, Vol 1, Issue 25

[Ilja Schmelzer]

>  1) an individual standing on the earth would have time progressing faster
> at his head than his feet (due to gravitational time dilation). How can a
> physical object be in two time frames? When blood flows in your body, does
> it move from the past to the future and vise versa? Seems logically
> preposterous.

And that's why even in standard GR all these frames play no longer any
role.  In GR, you have systems of coordinates.

And you have "proper time",  which is a bad English translation of the
German "Eigenzeit",  sort of "private time" or so, which is simply
clock time.

Once sufficiently accurate clocks at your foot and your head show
different results, such is life.  What do you have to object?   It is
a claim about what some clocks measure.  It has nothing at all to do
with logic or so.  The philosophical idea that "time is what clocks
measure" is, of course, to be rejected as positivistic nonsense.