# Planck time

Natural interval of time that can be obtained by combining the
fundamental natural constants that govern space-time, the strength of
gravity and the quantum world: the gravitational constant, Planck's constant and the speed of light. It amounts to about 5·10^{-44}
seconds and is the time it takes light to traverse one Planck length's worth of distance.

[Problems reading expressions such as 10^{-44}?
See exponential notation.]

At such time scales - for instance: at cosmic time comparable to the Planck time in the big bang models - both the effects of quantum theory and those of general relativity should become important, in short: such time intervals and what happens in them can only be described adequately using a theory of quantum gravity.

Compare: Planck length, Planck energy, Planck mass.