Figure 26-6: The Four Forces and the Standard Model (a) Gravitation is dominant on the scales of planets, star systems, and galaxies, while (b), (c) the strong, electromagnetic, and weak forces hold sway on the scale of atoms and nuclei. (d) The Standard Model describes the particles involved in the electromagnetic, weak, and strong forces. Bosons transmit the different forces; the photon transmits the electromagnetic force between charged particles (holding electrons in atoms); the gluon transmits the force between quarks (holding together atomic nuclei); and the intermediate vector bosons (Z,W) transmit the weak force (resulting in certain radioactive decays). These are all the known fundamental particles found in nature.