Why was the ether medium known as a hypothetical medium?

The ether medium, often referred to simply as "ether," was a hypothetical concept in the field of physics that was proposed in the 19th century to explain the propagation of electromagnetic waves, such as light. It was envisioned as a substance that permeated all of space and served as the medium through which electromagnetic waves traveled, similar to how sound waves travel through air or water waves travel through water. However, the concept of the ether was eventually discarded for several reasons:

Lack of Experimental Evidence: Despite its widespread acceptance as a theoretical construct, scientists could not detect or measure the existence of the ether through experiments. Attempts to measure the Earth's motion through the ether (via the Michelson-Morley experiment, for example) yielded null results, casting doubt on the ether's existence.

Special Theory of Relativity: Albert Einstein's special theory of relativity, published in 1905, provided an alternative framework for understanding the behavior of light and electromagnetic waves. According to this theory, the speed of light is constant in all inertial frames of reference, and there is no need for a medium like the ether to explain its propagation. This theory successfully explained many phenomena that were problematic for the ether hypothesis.

General Theory of Relativity: Einstein's general theory of relativity, published in 1915, provided a comprehensive framework for understanding gravity. In this theory, gravity is described as the curvature of spacetime itself, rendering the concept of the ether unnecessary for explaining gravitational interactions.

Quantum Mechanics: The development of quantum mechanics in the early 20th century further reshaped our understanding of the fundamental nature of the universe. Quantum field theory, which describes electromagnetic interactions, does not rely on the concept of a physical ether.

As a result of these developments in physics, the concept of the ether was gradually abandoned. It became clear that there was no need for a hypothetical medium to explain the behavior of electromagnetic waves and other physical phenomena. Instead, our modern understanding of physics is based on the principles of relativity and quantum mechanics, which have successfully explained a wide range of phenomena without invoking the concept of the ether.