This interactive demonstration compares the rate of the passage of time on an Earth clock versus the rate of the passage of time on a spaceship clock, the ratio of which is given by $\gamma$. Use the slider to set the rocket speed and press start. The slowing of time is hardly noticeable at speeds that are much less than $c$. But when the spaceship moves at speeds close to $c$, the slowing becomes dramatic. Take advantage of the pause function to compare the clock readings at different speeds.