Simply put, the relationship between physics and metaphysics is that they are two different methods of engaging with and attempting to describe reality. These two disciplines have not always existed harmoniously, as metaphysics deals with what its practitioners — usually philosophers and theologians — consider to be beyond the realm of science and sometimes to supersede scientific knowledge. In the modern era, many people have attempted to draw links between physics and metaphysics. These links have limited support within the mainstream scientific community.
The Greek word meta can mean either "after" or "beyond." Metaphysics is a term coined by Aristotle, who used it to mean simply the facts he wrote after he wrote about physics. In modern usage, however, metaphysics has come to refer to the study of objects outside the scope of purely scientific knowledge. The central questions of metaphysics include questions about ontology, the study of existence, and epistemology, the study of how humans acquire knowledge.
In the Western world prior to the scientific revolution, metaphysics was considered the primary source of knowledge about the world. Any theories in physics that seemed to contradict metaphysical knowledge — in this case religion — was considered heretical. The most famous example of this conflict between physics and metaphysics was in the life of the 16th century scientist Galileo Galilei, who proposed that Earth revolved around the sun, rather than the other way around. He spent much of his life under house arrest as a result of this belief.
Since that time, however, there has been a greater acceptance of scientific ideas that may seem to contradict experiences and metaphysical beliefs. The work of Galileo and of later physicists, such as Isaac Newton, has held up relatively well under further scrutiny. As a result, of many metaphysicists are willing to modify their beliefs, without fully discarding them, in response to scientific advances.
The discovery of quantum particles, special relativity and other modern physics phenomena have caused many people to re-evaluate their understandings the relationship between physics and metaphysics. Quantum particles, unlike larger units of matter, behave in ways that are unpredictable and that stretch preexisting categories of light and matter. Some theorists have argued that the existence of quantum particles negates deterministic metaphysics, though others disagree. Many people have drawn ideas from modern physics about the interconnectedness of all objects, which may inform their metaphysical assumptions or spiritual experiences. Most scientists, however, regard these simply as metaphors rather than as realities.