Exchange Particles and Interactions

Every force in nature operates through the exchange of particles. When two charged particles repel each other, they do so not by some mysterious "action at a distance" but by exchanging virtual photons between them. This idea — that forces are mediated by exchange particles (also called gauge bosons) — is one of the central pillars of the Standard Model.

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The Four Fundamental Forces

All interactions in nature can be attributed to four fundamental forces:

Force	Relative Strength	Range	Acts On	Exchange Particle
Strong nuclear	1	~10⁻¹⁵ m (~3 fm)	Quarks (and indirectly hadrons)	Gluons (g)
Electromagnetic	~10⁻²	Infinite (∝ 1/r²)	All charged particles	Photon (γ)
Weak nuclear	~10⁻⁶	~10⁻¹⁸ m	All quarks and leptons	W⁺, W⁻, Z⁰ bosons
Gravitational	~10⁻³⁹	Infinite (∝ 1/r²)	All particles with mass/energy	Graviton (hypothetical)

The Strong Nuclear Force