Free-Fall Frame Insight for Gravitation
Einstein recognised that an observer in sufficiently small free fall can describe local physics without an apparent gravitational force, an insight that became central to his equivalence principle.
Albert Einstein · Event
Einstein recognised that an observer in sufficiently small free fall can describe local physics without an apparent gravitational force, an insight that became central to his equivalence principle.

Einstein recognised that an observer in sufficiently small free fall can describe local physics without an apparent gravitational force, an insight that became central to his equivalence principle.