On the other hand, the effects are very important when the velocities are high enough. Suppose an alien spaceship traveling at $0.9c$ towards Earth fires a missile at the planet with speed $0.2c$ relative to the ship. According to the Newtonian addition of velocities, a stationary observer on Earth would see the missile traveling at $1.1c$, which is impossible, since it would arrive before the observer even saw it coming! Using the relativistic formula, however, we actually see the missile coming at:
$uequals;\frac{0.9cplus;0.2c}{1plus;\frac{\left(0.9\right)\left(0.2\right){c}^{2}}{{c}^{2}}}equals;0.93c$,
which is a much more reasonable speed, and would at least give us time to blink before being obliterated - assuming we were all glued to our telescopes when it happened.