No, Quantum Field Theory (QFT) is not a revisiting of the concept of "ether." The idea of the ether was a hypothetical medium that was once postulated to exist as a medium through which light and other electromagnetic waves could propagate. It was suggested as an explanation for the wave-like nature of light and the lack of a medium for its propagation.
However, the concept of the ether was eventually abandoned due to experimental results, including the Michelson-Morley experiment in 1887, which failed to detect any evidence of such a medium. Instead, the theory of special relativity, developed by Albert Einstein, provided an alternative explanation for the behavior of light and eliminated the need for an ether.
QFT, on the other hand, is a theoretical framework that combines quantum mechanics and special relativity to describe the behavior of elementary particles and their interactions. It does not rely on the concept of an ether as a medium for the propagation of particles or fields. In QFT, particles are described as excitations of quantum fields that permeate all of space, and interactions between particles are mediated by the exchange of other particles.
While QFT and the ether concept may share some superficial similarities in terms of postulating a medium, they are fundamentally different. QFT is firmly grounded in modern physics and has been extensively tested and validated through numerous experiments and observations. It provides a mathematical framework that accurately describes a wide range of phenomena, including particle interactions, particle creation and annihilation, and the behavior of quantum fields.