Albert Einstein did not change the term "ether fabric" to "spacetime fabric." In fact, he played a crucial role in discarding the concept of the luminiferous ether, which was a hypothetical medium thought to permeate space and serve as a medium for the propagation of light.
During the late 19th and early 20th centuries, there was a prevalent belief among physicists that light waves required a medium, the ether, to propagate through. However, experiments such as the Michelson-Morley experiment in 1887 failed to detect any evidence of the ether. This experimental result posed a challenge to the prevailing view.
Einstein's theory of special relativity, published in 1905, provided a different understanding of the nature of space and time. He showed that the laws of physics are the same in all inertial reference frames, and the speed of light in a vacuum is constant for all observers, regardless of their relative motion. In special relativity, there is no need for a separate medium like the ether to transmit light waves.
Einstein's theory of general relativity, published in 1915, further revolutionized our understanding of space, time, and gravity. General relativity describes gravity as the curvature of spacetime caused by the presence of mass and energy. It introduced the concept of a unified spacetime fabric, where the geometry of spacetime is influenced by the distribution of matter and energy.
In this framework, spacetime itself becomes the stage on which the events of the universe unfold. The curvature of spacetime determines the paths followed by particles and the propagation of light. It is important to note that spacetime is not considered an "absolute frame" but rather a dynamic framework that can be influenced by the presence of mass and energy.
So, while Einstein's work did bring about a significant shift in our understanding of space, time, and the propagation of light, he did not replace the term "ether fabric" with "spacetime fabric." Instead, he provided a framework that eliminated the need for the concept of the ether altogether.