@layman,
layman wrote:
Well, Lava, you are falling into the trap created by the long-discredited "positivistic" philosophy of science. The naive idea there is that "time is what a clock measures."
Time doesn't exist except as clock-motion. Really there is no such thing as 'time' outside the motion of various moving systems, all of which can be considered 'clocks,' if their motion is regular. The Earth's orbit is a clock, as is its rotation, etc. Einstein writes about 'clocks of equivalent construction' or something like that to denote that you can have two clocks that function in the same way but can be moved at different speeds or into different gravitational situations, but technically any system of regular motion can be used as a 'clock.'
There is nothing outside a clock causing it to move, though. A quartz watch moves because the battery drains through the crystal at a regular rate. Atomic clocks move because the isotope decays at a regular rate. Pendulums swing at a regular rate. All these different forms of motion are caused by the forces and energy that make the parts of the clock move; not by something external called 'time' that influences them from outside themselves.
Quote:Why it's true that clocks are specifically designed to measure time, the "thing" they are measuring is not a clock. Time is merely an abstract concept. As such it doesn't change with clock rates. I will repeat this example, which I stated earlier, to help illustrate the the difference.
Let's say you have a watch with a waning battery that only registers the passage of 55 minutes of time in an hour.
Does that mean that only 55 minutes have passed (because that's what the clock (mis)measured)? No, it doesn't. An hour has still passed.
Would it be proper to say that "only 55 minutes have passed for "it" (the slow clock)? No, it's still an hour, whatever the slow clock "thinks."
The only reason an hour remains an hour is because there is some other clock, maybe only a hypothetical ideal one, that elapses correctly. The assumption is that a good-functioning clock keeps time in a regular way and doesn't deviate from its pattern. So a watch with a waning battery is deviating from its ideal functioning, and that's why it is running slow. If the battery is renewed and everything else is functioning properly, 1 hour = 1 hour on that clock or any other clock like it that's running properly.
Quote:But how do we know what a real "hour" is? We do it by setting a standard for the elapse of time. Time would indeed be meaningless if there were no standard. If every clock on the planet which happened to be running at a different rate (including those which are stopped) had it's "own standard" for time, there could never be any standard whatsoever. This is the mistake that SR makes. It creates an infinite number of "standard" times, not all of which can be "correct," but which are nonetheless all said to be correct. If everything is the "standard" then there is no standard, and the whole concept of time is totally meaningless.
The standard is whatever clock is chosen and/or accepted as a standard. This discussion isn't about the politics of choosing which clock and/or method of comparing multiple clocks gets used as a standard for 'Time.' The only point I was making is that there is no 'Time' outside of individual clocks that is causing clocks to run. Clocks run because of their internal mechanics and the forces and energies that make them operate. That's all.
So when two clocks of equivalent function are accelerated relative to each other, or when one is in a different gravitational situation than another, and an observer can see them elapsing at different rates despite their functioning properly, that can be interpreted as a change in the rate at which time elapses, but you have to realize that it's the same observer watching both clocks moving at different rates. There could be an observer somewhere else that observes the ratio of time between the two clocks differently, e.g. because they are accelerating in a different direction relative to the two observed clocks.
