A simple pendulum is placed at a place where its distance from the earth’s surface is equal to the radius of the earth. If the length of the string is \( 4 \, \text{m}\), then the time period of small oscillation will be ________ \( \text{s} \).
\([ \text{take } g=\pi^{2} \, \text{m s}^{-2} ]\)