A time scale specifies divisions (scale) of time and possibly an epoch that marks the time when the time scale began ("time zero").

• A time standard is a specification of either the rate at which time passes, or points in time, or both.
• A duration is a quantity of time.

• The geological time scale divides up the history of Earth into scientifically meaningful periods.

• In astronomy and astrophysics:
  • A dynamical time scale either (in stellar physics) measures the length of time over which changes in one part of a body can be communicated to the rest of that body, or (in celestial mechanics) is a realization of a time-like argument based on a dynamical theory.
  • The nuclear time scale estimates the lifetime of a star based solely on its rate of fuel consumption.
  • The thermal time scale estimates the lifetime of a star once its fuel reserves at its center are used up or if they were to disappear.

• In cosmology and particle physics:
  • The Planck time is the time scale beneath which quantum effects are comparable in significance to gravitational effects. Neither general relativity nor quantum field theory adequately describe physics at the Planck time scale.

• In mathematics:
  • Time scale calculus is the unification of the theory of difference equations with differential equations.

• In music:
  • A rhythm is a temporal pattern of events.
  • Time scale (music), divides up music into sections based on the scope.

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