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The basic forces in nature
Contemporary Physics Education Project

Fundamental Forces

The interactions in the Universe are governed by four forces (strong, weak, electromagnetic and gravitational).

Physicists are trying to derive a unified theory that would describe all the forces in nature as a single fundamental law. So far they have succeeded in producing a unified description of the weak and electromagnetic forces, but a deeper understanding of the strong and gravitational forces has not yet been achieved.

Quantum physics describes the mutual effect of forces on particles by the "exchange" of other particles. For example, electrically charged particles attract or repel each other by emitting and absorbing photons, which carry the electromagnetic interaction.

FUNDAMENTAL FORCES

Interaction Relative Strength Range Mediating Particle
Strong 1 Short Gluon
Electromagnetic 0.0073 Long Photon
Weak 10-9 Very Short W,Z
Gravitational 10-38 Long Graviton

Table courtesy of University of Guelph, Guelph, Ontario (Cananda)

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF