that states that all events can be model
ed from within independant inertia
of reference and still yield the same result.
IE: a ball thrown from point
A to point
B strikes B. When obsereved by a moving vertex
C may have a different velocity
when observed from A but the net force
on B is observed as the same from either A or C.
In really small words:
It don't hurt you more
run after he