- #1

Kashmir

- 468

- 74

*Gravity*

"An observer in an inertial frame can discover a parameter ##t##with

respect to which the positions of all free particles are changing at constant rates.

This is time"

Then goes on to say

"Indeed, inertial frames

could be defined as Cartesian reference frames for which Newton’s first law holds

in the form ##\mathbf{\ddot r}=0##

Using the laws of mechanics, an observer in an inertial frame can construct a

clock that measures the time ##t##. For instance, the position of one free particle could

be used to measure ##t##, since its position changes at a constant rate in ##t##"

Using the position of one free particle to measure time, how does that guarantee that for other free particles this definition of time leads to ##\mathbf{\ddot r}=0##