This thesis discusses two key topics: strangeness and charge symmetry violation (CSV) in the nucleon. It also provides a pedagogical introduction to chiral effective field theory tailored to the high-precision era of lattice quantum chromodynamics (QCD). Because the nucleon has zero net strangeness, strange observables give tremendous insight into the nature of the vacuum; they can only arise through quantum fluctuations in which strange–antistrange quark pairs are generated. As a result, the precise values of these quantities within QCD are important in physics arenas as diverse as precision tests of QCD, searches for physics beyond the Standard Model, and the interpretation of dark matter direct-detection experiments. Similarly, the precise knowledge of CSV observables has, with increasing experimental precision, become essential to the interpretation of many searches for physics beyond the Standard Model. In this thesis, the numerical lattice gauge theory approach to QCD is combined with the chiral perturbation theory formalism to determine strange and CSV quantities in a diverse range of observables including the octet baryon masses, sigma terms, electromagnetic form factors, and parton distribution functions. This thesis builds a comprehensive and coherent picture of the current status of understanding of strangeness and charge symmetry violation in the nucleon.

Dramatic progress has been made in all branches of physics since the National Research Council's 1986 decadal survey of the field. The Physics in a New Era series explores these advances and looks ahead to future goals. The series includes assessments of the major subfields and reports on several smaller subfields, and preparation has begun on an overview volume on the unity of physics, its relationships to other fields, and its contributions to national needs. Nuclear Physics is the latest volume of the series. The book describes current activity in understanding nuclear structure and symmetries, the behavior of matter at extreme densities, the role of nuclear physics in astrophysics and cosmology, and the instrumentation and facilities used by the field. It makes recommendations on the resources needed for experimental and theoretical advances in the coming decade.

This work is a translation of the German edition "Der Nukleonenspin als Ursache der starken Wechselwirkung". (Dec. 2020). The strong interaction is supposed to describe the forces which are active in the atomic nucleus between the nuclear building blocks. Until today, however, it has not been possible to design a theory free of contradictions. Instead, in the 1970s, the theory of "quantum chromodynamics" emerged, in which the name itself is based on an analogy. Just like the "color charges" mentioned as cause of the interaction. The question is only: Analogy to what and due to which energy? Because either it refers to the electric energy, then there would have to be some kind of electric parallel energy, but this is nonsensical. Or it doesn't refer to the electric energy, then it must be a form of energy which already exists. But quantum chromodynamics makes no statement about this. This QCD theory standing on shaky feet thus virtually challenges the contradiction. In order to oppose this very artificial theory with a down-to-earth one, it is important to keep in mind the basics of the known interactions. All particle systems can build up only if their particles have besides their energy also an opposite property by which they can interact. The simplest system is a binary system, e.g. a common salt crystal. The opposite properties are the electrically positive and negative charge of the ions. But which opposite property enables an interaction of the nucleons? It cannot be an electric charge. The astonishing answer to this question is given in this paper at the end. It also becomes clear that quantum chromodynamics is a fallacy. For a better understanding, contents of earlier publications of the author are partly included.