On the Definition of Vacuum the Physical Nature of Fields and the Analysis of Conceptual Confusion

In modern physical literature and popular science contexts the term vacuum carries multiple incompatible definitions and most disputes in this field stem from the confusion of terminology rather than conflicts in experimental observations. This paper distinguishes three hierarchical definitions of vacuum engineering vacuum ideal logical vacuum and quantum field theoretical vacuum and clarifies the boundary between material solid particles traveling photons and fields. A field is a descriptive tool for the scope and distribution of force effects rather than an independent physical substance. Even if all material solid particles such as atoms molecules protons neutrons and electrons are removed from cosmic space photons still travel continuously through the space. This paper analyzes the origin of the popular claim that vacuum is not empty distinguishes objective experimental phenomena from theoretical model hypotheses clarifies the instantaneous action at a distance characteristics of the three fundamental force fields gravitational field electromagnetic field and strong interaction field and states clearly that photons do not act as field sources nor interact with the three force fields. By comparing with the mainstream hypothesis that interactions are transmitted via intermediate particles this paper points out that the failure to declare definition switches in academic outputs leads to public cognitive confusion. Clarifying term definitions is the premise of rational physical discussion and helps reduce unnecessary debates caused by wording ambiguity.