The 4 Fundamental Forces

There are only four fundamental kinds of forces in the universe:

  1. The gravitational force: how massive objects interact with one another.
  2. The electromagnetic force: how charged objects interact with one another. Everyday forces---tension, friction, and the normal force---all stem from electromagnetic interactions.
  3. The strong force: holds nuclei together.
  4. The weak force: associated with radioactivity.