Classical Relativity in a Nutshell

Classical Relativity comes from two words “classical” and “relativity”. According to the Oxford Dictionary, classical means representing an exemplary standard; traditional and long-established in form or style. While relativity means the absence of standards of absolute and universal application. Classical relativity is an old and long established theory proposed by Galileo and Newton that relates the relative motion of objects in different reference frame.

Imagine standing on the side walk of a road and looking at two of your friends standing at the back of a pickup truck moving with a certain constant velocity. In your perspective, what would you see and imply about both your friend’s motion? you would see them both moving with the same velocity as the pickup truck. But in their perspective, since the pickup truck is moving with a certain constant velocity, they would imply that they are not moving relative to each other. How can this be possible? It’s possible because motion is relative. So we are in motion and at rest in the same time because of the two different reference frame.

Meaning there are no such thing as absolute motion or absolute rest since it’s just a matter of perspective but behind that lies absolute time. Although different in perspective, but the law of mechanics must be the same in both reference frame. This is called the principle of classical relativity. Classical relativity only works in the limit of objects having speed far below the speed of light. For objects near the speed of light, we must consider a more general theory.