Alfonso says...

On 25/03/11 14:17, Daryl McCullough wrote:
Alfonso says...

To distinguish the three meanings of 'time' I will re-express the set I
in the following not unnatural ways:
Set III
(a) The journey occurred in eternity.
(b) The instant of starting was 1 o'clock.
(c) The duration of the journey was 2 hours." Dingle

Note that only (c) has units of seconds. I think that part of the
problem is that we are all familiar with clocks# and think of them as
something which tells time in hours minutes and seconds. In scientific
terms we should perhaps not use the term clock but "duration meter" -
envisaging something with a digital reading which increments at some
interval 1/10^n seconds. The larger n then the better the resolution -
which is started by one detected event and stopped by another event.
Your statement:
"What time is, is what a clock locally at rest measures".
Becomes
What time is, is what a "duration meter" locally at rest measures.
In terms of my scenario the only interval which the duration meter can
measure is the interval between the ticks - the reciprocal of which is
the frequency of the ticks.

Right. Time in the sense of (b), which is a way of assigning
labels to events, requires two things: (1) a clock for measuring
durations, and (2) an initial setting.

Under what circumstance would you consider an "initial setting" essential?

To say that "It is now 1:00 p.m." requires not just a clock, but a
convention for when you set the clock to 12:00 a.m.

On the other hand, to say "It is 2 hours and 15 minutes since sunset"
does not require an initial setting.

--
Daryl McCullough
Ithaca, NY