In Einstein's theory of relativity, the length of an object depends on its velocity. If $L_{0}$ is the length of the object at rest, $v$ is the object's velocity and $c$ is the speed of light, the Lorentz contraction formula for the length of the object is $L=L_{0} \sqrt{1-v^{2} / c^{2}} .$ Treating $L$ as a function of $v,$ find the linear approximation of $L$ at $v=0$.