Relativity, as described by Einstein, challenges our everyday understanding of motion. Forget what you know about velocities simply adding up. Instead, we have to rely on some nifty equations. But don't panic! We've got spaceships, Jean and Phillipe, and even some math to help you out.

• Galilean Relativity: This is your everyday, simple kind of relativity. In this view
• If a spaceship moves at uA​ in frame A and frame B moves at v relative to frame A, then the spaceship's velocity in frame B is -uB ​= uA ​− v.
• Einstein Relativity (Special Relativity): Things get spicy!
• If our spaceship in frame A goes at the speed of light, and the observer in frame B sees it going the opposite way, the speed would look faster than light. That's a big NO-NO in Einstein's world.

To make sense of these super-fast velocities, we use the Lorentz transformations: uB ​=\(u_B = \frac {x^I}{t^I} = \frac {γ(x - vt)}{γ{(t - vx / c^2)}}\)​ Where

• ′x′ and ′t′ are the distance and time in frame B.
• γ (gamma) is the Lorentz factor.

This leads to our superstar equation for relativistic velocity addition - 2uB​=1−c2uA​v​uA​−v​