Planck time

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The time taken for a photon (travelling at the speed of light c) to move through a distance equal to the Planck length. It is given by tP = √(Għ/c5), where G is the gravitational constant and ħ is the rationalized Planck constant. The value of the Planck time is of order 10−43 s. In the big-bang cosmology, up until a time tP after the initial instant, it is necessary to use a quantum theory of gravity to describe the evolution of the universe.

Subjects: Physics.

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