Physics is often defined as the study of Matter in Motion. This is part of the reason that physics relates to the other sciences in the way it does: all other sciences observe that which is made of matter, and in motion.
The phrase 'matter in motion', requires us to define matter and motion. Presently, motion is considered the trajectory of an object through Space-Time.
While the definitions of spacetime have changed throughout the years, the current definition, is that of [[General Relativity],] which is geometric in nature.