The Theory of relativity states that if at rest someone views a light ray enter at an angle \(\theta\) (theta) relative to some direction and if we move into this direction, then at the same place we view the same light ray at a smaller angle \(\theta'\) which satisfies the equation
$$\tan \frac{\theta'}{2} = \sqrt{\frac{c-v}{c+v}} \tan \frac{\theta}{2}$$
In this equation \(v\) is our velocity and \(c\) is the velocity of light in the vacuum.
