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Despite the complexity of the universe, all matter is made up of a limited number of particles, and the way in which these particles interact with one another can be reduced to no more than four distinct interactions.
Cosmology Series
  1. What is Cosmology?
  2. The Speed of Light
  3. Redshift and Blueshift
  4. What is the Cosmic Microwave Background Radiation?
  5. Cosmic Scale Factor and Expansion of the Universe
  6. The Physics Governing the Universe
  7. The Nature of Light
  8. The Four Forces in the Universe
  9. The Expansion of the Universe

Strong Interaction

The strong interaction is the force binding quarks within a particle or atomic nucleus. It is also responsible for the force between the nucleons in a nucleus. The strong interaction acts on a very small range it becomes negligible on distances greater than 10-15m between particles.

Electromagnetic Interaction

The electromagnetic interaction is a force acting between all electrically charged particles. It keeps, for example, the electrons bound to the nucleus of an atom. The electromagnetic interaction acts over an infinite distance but is over 100 times weaker than the strong interaction on a comparable scale.

Weak Interaction

There are particles which are not affected by the strong interaction, but interact with one another and other particles very weakly. The strength of the weak interaction is only 10-14 times that of the strong interaction and is present only in a very short range of 10-18m, so it plays a role only at the nuclear and sub-nuclear level.

Gravitational Interaction

The gravitational interaction is the weakest of the fundamental interactions and occurs between all particles to an infinite distance. Its strength is only 10-38 times that of the strong interaction on the same spatial scale.

Nevertheless, gravity is the force which governs the development of the universe at the present epoch.

Tutorial Series

This post is part of the series Cosmology. Use the links below to advance to the next tutorial in the couse, or go back and see the previous in the tutorial series.

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