Relativistic Length: The length of an object as measured by an observer in relative motion to that object, which appears shorter than the object's length as measured by an observer at rest with respect to the object.
Time Dilation:The phenomenon where time appears to pass more slowly for an object in motion relative to an observer at rest, as described by Einstein's theory of special relativity.
Relativistic Velocity: The speed of an object relative to an observer, which is limited by the speed of light and affects the object's length and the passage of time as observed by the viewer.