This is a summary of the different interactions, their force carrier particles, and what particles they act on: Which fundamental interaction is responsible for: Friction? Answer Friction is caused by residual electromagnetic interactions between the atoms of the two materials. Nuclear bonding? Answer Nuclear bonding is caused by residual strong interactions between the various parts of the nucleus. Planetary orbits? Answer The planets orbit because of the gravity that attracts them to the sun! Even though gravity is a relatively weak force, it still has very important effects on the world. Other questions: Which interactions act on neutrinos? Answer Weak and Gravity Which interaction has heavy carriers? Answer Weak (W+, W-, and Z) Which interactions act on the protons in you? Answer All of them. Which force carriers cannot be isolated? Why? Answer Gluons, because they carry color charge themselves. Which force carriers have not been observed? Answer Gravitons (Gluons have been observed indirectly.)