The collection of quantum fields, as described by modern physics, is fundamentally different from the concept of the luminiferous aether that was rejected by the Michelson-Morley experiment. Here are the key differences:
Nature of the medium: The luminiferous aether was proposed as a hypothetical medium permeating all of space, through which electromagnetic waves were thought to propagate. It was envisioned as a material substance with specific properties. In contrast, quantum fields are not material substances but rather mathematical constructs that describe the behavior and interactions of particles and forces. Quantum fields are associated with fundamental particles and their excitations, but they are not considered a physical medium through which waves travel.
Absolute frame of reference: The aether theory implied the existence of an absolute frame of reference, meaning there was a preferred reference frame against which all motion could be measured. The Michelson-Morley experiment aimed to detect the motion of the Earth relative to this aether, expecting to observe a change in the speed of light depending on the direction of motion. However, the experiment's results showed no such variations, leading to the rejection of the aether theory. In contrast, quantum field theory, as part of modern physics, is based on the principles of relativity, which do not require or allow for the existence of an absolute frame of reference.
Localized excitations: Quantum fields, such as the electromagnetic field or the Higgs field, are defined at every point in space. They are associated with localized excitations or quanta (particles) that can propagate and interact within the field. These particles have quantized properties, such as energy, momentum, and spin, and their behavior is governed by probabilistic rules described by quantum mechanics. The aether theory, on the other hand, did not involve localized excitations or quantized properties but was conceived as a continuous and homogeneous medium.
Experimental evidence: The Michelson-Morley experiment provided empirical evidence that contradicted the predictions of the aether theory. The null result of the experiment, indicating the absence of an aether wind, suggested that the concept of a stationary aether was unnecessary to explain the behavior of light. In contrast, quantum field theory, including its successful predictions and compatibility with experimental observations, has provided a robust framework for understanding fundamental particles and their interactions.
In summary, the collection of quantum fields in modern physics is a mathematical framework that describes the behavior of particles and forces, while the aether theory was a now-discredited hypothesis of a material medium for the propagation of light. The rejection of the aether theory by the Michelson-Morley experiment played a crucial role in the development of Einstein's theory of special relativity, which forms the foundation of modern physics.