What Does UTime" Mean?--A. A. MERRILL. Fifteen years ago I published an explanation of the fact that clocks can not possibly measure time. To measure, means to correlate a number with the thing measured which can be done only with space. That is why all measuring instruments must have space scales either linear or angular and it is also why the language of physics has to take the form of a geometry.
Set up a pendulum to swing in a north and south direction with a pencil at its lower end. Place a paper so that it can be moved from east to west and so that the pencil marks the paper when the pendulum passes its lowest point. Start both the pendulum and paper moving and soon you will see a series of marks on the paper. Now I say: Between the making of any two of those marks a time interval elapsed and for physics surely all that that can possibly mean is that while the pendulum and the paper were moving all other bodies in the universe were also moving. A time interval for physics can only mean all bodies move, or there is no absolute rest, but for human living a time interval means the accumulation of experience and memories, the two meanings being entirely different.
While it has become a habit, it is nevertheless an error to call the "t" of physics "time" because the "t" of physics refers only to some privileged "motion" functioning as a clock. It is motion, not time that is relative and that is old in Newton.