Yes, Albert Einstein's work on the theory of relativity built upon and expanded upon Newtonian mechanics. While Einstein's theories of special and general relativity introduced profound conceptual shifts and modifications to our understanding of space, time, and gravity, they were not a complete departure from Newtonian mechanics. Instead, they can be seen as refinements and extensions that provide a more accurate and comprehensive description of the physical world.
In the case of special relativity, Einstein's theory was developed to reconcile discrepancies between the laws of electromagnetism and Newtonian mechanics. Special relativity incorporates the principle of the constancy of the speed of light and introduces the concept of spacetime, where time and space are unified. While special relativity introduces significant changes to the way we perceive time, length, and simultaneity, it still aligns with Newtonian mechanics under everyday conditions when speeds are much smaller than the speed of light.
In the case of general relativity, Einstein sought to incorporate gravity into the framework of special relativity. He was influenced by Newtonian gravitation but realized that it had limitations and was inconsistent with the principles of special relativity. Einstein's general theory of relativity proposed a new understanding of gravity as the curvature of spacetime caused by mass and energy. In the limit of low speeds and weak gravitational fields, the equations of general relativity reduce to Newton's laws of motion and his law of universal gravitation.
Therefore, while Einstein's theories of relativity went beyond Newtonian mechanics in terms of their scope and conceptual framework, they were built upon and incorporated the principles of Newtonian mechanics in appropriate limits and situations.