 Lorentz factor

For a relative speed $0\le v<c$, the Lorentz factor is

At $v=0.6c$, $\gamma =1/\sqrt{1-0.36}=1/0.8=1.25$. Thus a moving clock accumulates $0.8$ seconds of proper time per laboratory second, and a parallel moving rod has $0.8$ times its rest length. The Lorentz factor approaches one at small speed and grows without bound as $v$ approaches the speed of light; a massive object's rest frame never requires a boost at $v=c$.

The Lorentz factor, denoted by the Greek letter gamma (γ), is a factor that arises in the theory of special relativity. It describes how much time, length, and relativistic mass increase as an object approaches the speed of light.