Definition of arrow of time or time's arrow in English:

arrow of time (or time's arrow)

The direction of travel from past to future in time considered as a physical dimension.
More example sentences
  • In other words, in the microworld, there is no intrinsic arrow of time, distinguishing the future from the past.
  • In the late twentieth century, an arrow of time may have been discovered at the subatomic level.
  • There was a conference on Wheeler Feynman electrodynamics and the arrow of time, in 1963.
See parent entry: arrow

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