Nucleus
The nucleus is the small, dense, positively charged core of an Atom, containing essentially all of its mass and made of protons and neutrons.
The standard account
Rutherford inferred the nucleus in 1911 from the large-angle scattering of alpha particles by gold foil, identified the Proton in 1919, and Chadwick identified the Neutron in 1932. A nucleus is of order 10−15 m across — about five orders of magnitude smaller than the atom — so the atom is overwhelmingly empty on this picture. The number of protons fixes the chemical element; the number of neutrons fixes the isotope.
Something must hold like charges together against Coulomb repulsion at that separation, and the standard answer is the strong nuclear force, short-ranged and charge-independent, now understood as a residual effect of the colour force between quarks. The binding energy per nucleon rises to about 8.8 MeV near iron-56 and falls away on both sides, which is why both fusion of light nuclei and fission of heavy ones release energy. Two complementary models are used: the liquid-drop model, which gives the semi-empirical mass formula and describes fission well, and the shell model of Goeppert Mayer and Jensen (1949), which explains the "magic numbers" 2, 8, 20, 28, 50, 82 and 126 at which nuclei are unusually stable. That two such different pictures are both needed, and that no first-principles calculation of medium and heavy nuclei from quantum chromodynamics yet exists, is an acknowledged limitation of the mainstream account rather than a hidden one.
On this wiki
Category:Nuclear Structure collects roughly fifty pages proposing structured, geometric or electrodynamic nuclei in place of the strong force.
- Charles William Lucas and Joseph C Lucas argue in A Physical Model for Atoms and Nuclei, Part 2: Structure of the Nucleus that nuclear binding follows from a universal electrodynamic force between finite-size ring particles, dispensing with a separate strong interaction — a position shared with Common Sense Science and David L Bergman.
- Thomas N Lockyer's Vector Particle and Nuclear Models and Malcolm H MacGregor's work propose structured nucleons.
- Don Briddell models nucleons as field structures; Stoyan Sarg derives nuclear structure from his Basic Structures of Matter - Supergravitation Unified Theory - a new approach in Physics.
- Randell L Mills and Xavier Borg give further alternative nuclear treatments; Magic Numbers Derivation from Variable Phase Nuclear Model attempts to recover the shell-model magic numbers from a different starting point.
- Critique to the Models of Nuclear Physics, New Nuclear Model and Nuclear Alternative: Redesigning Our Model of the Structure of Matter state the general case against the standard models.
- The nuclear question connects directly to the Cold Fusion material here, since low-energy nuclear reaction claims require some account of how the Coulomb barrier can be crossed at ordinary temperatures.
A fair test of these models is whether they reproduce the binding-energy curve, the magic numbers and measured nuclear moments; the pages above vary a great deal in how far they attempt that.