Theoretical physics does not rely on the existence of an ether as postulated in Maxwell's theory. While Maxwell's original formulation of electromagnetism included the concept of the luminiferous ether, subsequent developments in physics, particularly Einstein's theory of special relativity, rendered the notion of an ether unnecessary.
Einstein's theory of special relativity, published in 1905, showed that the laws of physics, including electromagnetism, are consistent in all inertial reference frames without the need for a medium like the ether. Special relativity demonstrated that the speed of light in a vacuum is constant and independent of the observer's frame of reference, leading to the conclusion that electromagnetic waves do not require a material medium for their propagation.
As a result, modern theoretical physics, including the formulation of electromagnetism, is based on a more abstract framework that does not involve an ether. Electromagnetic phenomena are described by Maxwell's equations, which remain valid within the context of modern physics. Maxwell's equations provide a mathematical description of how electric and magnetic fields interact and propagate through space, without the need for an underlying medium.
It is worth noting that the concept of an ether was historically significant and played a role in the development of Maxwell's theory. The idea of an ether was proposed as a hypothetical medium to explain the propagation of electromagnetic waves and the phenomena of optics. However, with the advent of special relativity and subsequent experimental evidence, the concept of an ether as a physical medium was rendered unnecessary.
In summary, while Maxwell's original theory incorporated the concept of an ether, modern theoretical physics, including electromagnetism, does not rely on the existence of such an ether. The theoretical framework has evolved to accommodate new understandings, such as special relativity, which provides a more comprehensive and accurate description of electromagnetic phenomena.