Planck time

Planck time is usually noted t_P, symbol made of the latin letter t lowercase, initial of latin word tempus ("time"), in italic, followed to the right and subscript, by the latin letter P uppercase, initial of the last name of Max Planck.

Planck time is defined by :

${\displaystyle t_{\mathrm {P} }={\sqrt {\frac {hG}{2\pi {c^{5}}}}}={\sqrt {\frac {\hbar {G}}{c^{5}}}}={\frac {\ell _{\mathrm {P} }}{c}}}$ ,

where :

• ${\displaystyle \hbar }$  is the Planck constant ;
• ${\displaystyle G}$  is the gravitational constant ;
• ${\displaystyle c}$  is the speed of light in a vacuum ;
• ${\displaystyle \ell _{P}}$  is Planck length.

In the International System of Units, the recommended value ^[5] for the Planck time is :

${\displaystyle t_{\mathrm {P} }=5{,}391\ 247(60)\times 10^{-44}}$  s,

with a relative error of 10^-4.

• Planck length