motion of the bird. We know that all of these trajectories are changed; we do not know that the velocity or rate of speed of any particle of the bird’s body was increased or diminished. If Newton’s third law of motion, that action and reaction are equal, is true in the exact terms in which he stated it, then we must affirm that the speed of no particle was changed but only its trajectory. We do not see the astronomical motions of the bird nor its molecular motions. We do see the molar motions in flying from tree to tree and thus an illusion is produced that motion can be created or destroyed by the bird, and the persistence of motion seems to be a fallacy and the correlation of forces a fiction. We do not see the creation, continuance and annihilation of motion in the bird, but the deflection of astronomical and molecular motions as known by scientific investigation. This discussion is designed to show that motion is not a relation, but that one motion may be said to be related to another or related to any selected position.
V
Time is persistence and change, the persistence being absolute because it exists in the particle independent of other particles, and constant, for the particles cannot be annihilated. Change is relative, in that it inheres in the relations of the particles, and it is also variable, for particles are constantly changing their relations of position to each other by occupying a succession of positions. Thus time is absolute and relative, constant and variable.
The earth as a body changes the position of its particles by rotation upon its axis and thus passes
