Lorentz Transformation - describes how, according to the theory of special relativity, different measurements of space and time by two observers can be converted into the measurements observed in either frame of reference.
The above formula is used for calculating the changes that occur when objects approach the speed of light. An object in motion undergoes 3 relativistic changes: 1) an increase in mass, 2) a contraction in the direction of travel (Lorentz Transformation) and 3) A "slowing down" of time. (Time Dilation)
Views of spacetime along the world line of a rapidly accelerating observer in a relativistic universe. The events ("dots") that pass the two diagonal lines in the bottom half of the image (the past light cone of the observer in the origin) are the events visible to the observer.