Electromagnetic Force

Electromagnetism (aka: the electromagnetic force or electromagnetic interaction) is described by electromagnetic fields, and has innumerable physical instances including the interaction of electrically charged particles and the interaction of uncharged magnetic force fields with electrical conductors.

The electromagnetic force is the one responsible for practically all the phenomena one encounters in daily life above the nuclear (subatomic) scale, with the exception of gravity. Light, magnetism, and electricity are but a few of the many manifestations of the electromagnetic force that we experience every day.

Roughly speaking, nearly all of the forces involved in interactions between atoms can be explained by the electromagnetic force acting on the electrically charged atomic nuclei and electrons inside and around the atoms, together with how these particles carry momentum by their movement. This includes the forces we experience in "pushing" or "pulling" ordinary material objects, which come from the intermolecular forces between the individual molecules in our bodies and those in the objects. It also includes all forms of chemical phenomena.

Photons are the carriers of the electromagnetic force and particles that interact with the electromagnetic force are said to have a charge- positive or negative. This is a familiar property we encounter in magnets and batteries.

Strong Force (aka Color Force)

Also called the strong interaction, strong nuclear force, or color force, the strong force is the binding energy that ensures the stability of all ordinary matter. The strong force binds quarks, the fundamental particles of matter (fermions), into hadrons such as the proton and neutron, which in turn make up atoms and everyday matter. The strong force is carried by gluons, and can be appropriately thought of as the glue that holds matter together.

Most are familiar with the idea of particles having positive or negative electromagnetic charge— in batteries, magnets etc. Similarly, particles that interact with the strong force are said to have a property called &lsdquo;color charge”- Red, Blue, or Green. Color charge has nothing to do with visual color, but the name comes from reference to the way additive primary colors-Red, Green, Blue- mix. Particles that interact with the strong force “mix,” or react to each other in a metaphorically similar way to these primaries when they are combined, thus the term ‘color charge’ was chosen to represent this property.

Color Charge

The "color charge" of quarks and gluons has nothing to do with the visual perception of color. It simply means that these particles interact with the strong force (which is why the strong force is also called the color force). The idea of "color charge"; is used as a metaphor to explain complex interactions (mixings) between particles affected by strong force. Particles that interact with the strong force have a color charge of Red, Blue, or Green— based on the additive primary colors (primaries of light, not pigment). Antiparticles that interact with the strong force also have color—antired, antiblue, and antigreen (which would be better labeled cyan, yellow, and magenta, respectively, if properly following the RGB metaphor.)

Just as the three additive primaries— red, green, and blue combine together, or each with a respective complement— antired (aka:cyan), antigreen (aka: magenta), and antiblue (aka:yellow) to create white (colorless), particles with color charge behave the same way. A combination of three particles, one with red charge, another with green charge, and another blue charge, has a net color charge of zero (colorless); once a color neutral particle is formed, the strong force stabilizes and the particle is no longer affected by other color charged particles. Just as colors have complements, particles have corresponding antiparticles; the combination of color charged particle with its antiparticle (ex green particle with an antigreen antiparticle) also results in color cancellation (colorless: net charge of zero). All free particles have a color charge of zero.

Weak Force

The weak force, or weak interaction, is carried by W and Z Bosons and is responsible for both radioactive decay and nuclear fusion of subatomic particles. The range of this force is smaller than 1 fm and is 10^-7 times weaker than the strong force. Radioactive decay, also known as nuclear decay or radioactivity, is the process by which a nucleus of an unstable atom loses energy by emitting particles of ionizing radiation.

Nuclear Fusion is a reaction in which two or more atomic nuclei collide at a very high speed and join to form a new type of atomic nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy.

In essence, the weak force contrasts with the strong force in that it has to do with the instability, rather than the stability, of matter. The weak interaction is unique in that it allows for quarks to swap their flavor for another- i.e. the weak force is what allows quarks to decay from 3rd generation matter (Tops & Bottoms) to 1st generation matter (Ups & Downs). In addition, the weak interaction is the only fundamental interaction that breaks CP-symmetry.

Gravitational Force

Gravitation, which we experience on Earth as "gravity," is a force of attraction that acts between and on all physical objects with matter (mass) or energy. It is the natural phenomenon by which all physical bodies attract each other. It is most commonly recognized and experienced as the agent that gives weight to physical objects, and causes physical objects to fall toward the ground when dropped from a height.

It is hypothesized that the gravitational force is carried by a massless spin-2 particle called the graviton (a gauge boson) though this particle has yet to be discovered.