Top 10 Coolest Fundamental Interactions of Chemistry/Physics

In classical physics, gravity was simply a force that varied inversely with the square of the distance between two objects. It was simply an explanation for why we have a constant acceleration in freefall towards an object or why the Earth orbits the Sun. Albert Einstein took it to another level in 1915 with general relativity, as he explained that acceleration and gravitation were one and the same. Any body with energy and momentum could deviate the spacetime continuum in higher dimensions, which would reduce the progression of time under the greater influence of this deviation to keep the speed of light constant. This caused the acceleration towards a body that we observe as gravitation, as opposed to gravitation resulting from a force.

However, this could not be expressed in terms of quantum interactions. These laws state that, given that the geometry of the spacetime continuum is quantized at the smallest measurable units in the universe, the Planck units, the fundamental interactions of gravitation occur between the smallest possible unit of energy which can deviate the spacetime continuum. This phenomenon is known as quantum foam, and the fundamental gravitation between these points in the continuum is mediated by the exchange of virtual gravitons.

The graviton, however, is difficult to model, as the interaction in question involves a quantum loop. This is a phenomenon that cannot be expressed intuitively, as it is expressed in terms of higher dimensions. It appears that the graviton oscillates in a periodic pattern, which is a property that particles unlike the graviton are not expected to express. String theorists explain this by stating that fundamental strings oscillate in dimensions invisible to modern knowledge to display the properties of the graviton, and the mathematics of this will give a renormalization of the interaction. However, with the explanation being entirely mathematical and without experimental evidence, this model is... more

The strong interaction is aptly named. It is the strongest force in the universe, and without it, our universe would not exist as we know it. The strong force is mediated by gluons between quarks, the fundamental particles that make up hadrons such as protons and pions. Between baryons, it is mediated by a pion, which is unique as this does not involve a fundamental boson.

Quarks are distinguished from one another by the principle of color charge, where quarks have a specific color charge associated with them, its antiquark with its anticolor. The gluon mediates the color and anticolor charge associated with the quarks with which it interacts, meaning that eight types of gluon must exist in order to conserve color charge in any strong interaction. So, a specific gluon can only account for an interaction between two specific superpositions between the states of each of the two color charges in the interaction. For instance, the superposition of red with antigreen and green with antired.

The strong interaction is responsible for quark confinement. A quark is never isolated, as the energy required to separate two or more quarks is greater than the energy required for pair production of a quark-antiquark pair. The only conditions in which quarks are isolated are at ultra-high densities, in which the structure of the hadrons breaks down, which has only been confirmed to take place in a quark star.

The strong force is also responsible for the binding of atomic nuclei, as it attracts at distances greater than half a femtometer (it repels below this value to prevent the nucleus from collapsing in upon itself). However, given its short range and short half-life, the electrostatic repulsion between two hadrons of like charge is greater in apparent magnitude at distances greater than three femtometers. This is why a high energy input, at high temperatures and pressures, as well as quantum tunneling, is necessary to achieve nuclear fusion, where the... more

The one we've all heard of. Photons are more than simply corpuscles of light. They mediate the fundamental interactions between charged particles, making the positron attract the electron and making the proton repel the proton next to it.

Electric fields and magnetic fields were previously treated separately, but it was the work of Michael Faraday and James Clerk Maxwell that unified them. Faraday experimented with electricity and magnetism, and he noticed that if one could apply a magnetic field alongside an electrical current, he could deviate both the electric and magnetic fields present. The same could be done by applying an electrical field to a source of magnetic flux. This proposed that a force existed which would induce a change in magnetic flux from a change in an electrical current, and vice versa.

Maxwell expressed these phenomena mathematically to show that an electromagnetic field would flow from a positive to negative charge point, such that the energy within this electromagnetic field would not change unless acted upon externally. The observations and the mathematics concocted by Maxwell showed that these interactions were mediated by means of light. Therefore, light is an electromagnetic wave.

Light was later described in terms of particles when Planck suggested that light transfers its energy in discrete quanta, the energy of each corpuscle being directly proportional to the frequency of light. Einstein was the first to produce evidence of this with the photoelectric effect, where photons incident upon a metal surface interact one-on-one with electrons within the metal and trigger photoemission. This can only occur when the electrons have sufficient energy to be emitted. Only above certain frequencies can photoemission occur, it being independent of frequency unless two photons were to superpose, which cannot be explained by the wave theory of light.

This quantized transfer of energy expressed the fundamental... more

The weak interaction is responsible for the beta decay of nuclei and the breakdown of unstable configurations of quarks. It was first noticed in 1933 by Enrico Fermi that nuclei of a specific configuration would decay into a more stable configuration by releasing energy in the form of a charged lepton or antilepton and its corresponding antineutrino or neutrino. This process is mediated by the transfer of a W boson, which can be either positive or negative to conserve charge.

Negative beta decay occurs when a nucleus is unstable due to having too many neutrons. In this case, a down quark within a neutron emits a negative W boson, converting the down quark to an up quark and the neutron to a proton. The W boson then promptly decays into an electron and an anti-electron-neutrino.

Positive beta decay occurs when a nucleus is unstable due to having too many protons. Here, an up quark within a proton emits a positive W boson, converting the up quark to a down quark and the proton to a neutron. The W boson promptly decays into a positron and an electron-neutrino.

Neutral Z bosons exist to emit sufficient levels of energy from leptons, decaying into a particle-antiparticle pair of lower energy. We know that the weak interaction must be weaker than the strong interaction, as it would otherwise affect stable nuclei. Without the weak interaction, we would live in a world without nuclear decay, and the quantum property of strangeness would have no noticeable significance. We wouldn't know if the property existed.