fifth force

American  

noun

1. a theoretical force in nature in addition to the strong and weak forces, gravitation, and the electromagnetic force.

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fifth force British  

noun

1. a hypothetical non-Newtonian repulsive component of the force of gravity, postulated as an addition to the four known fundamental forces (gravitational, electromagnetic, strong, and weak)

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fifth force Scientific  

/ fĭfth /

1. Any of various hypothetical, very weak forces thought to cause bodies to repel each other. Such forces are occasionally considered as a solution to unexpected deviations in the measured value of the gravitational constant or to explain the apparent acceleration of very distant galaxies away from earth.

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Etymology

Origin of fifth force

First recorded in 1975–80

Example Sentences

See Examples For:

fifth force

That discrepancy excited physicists because it hinted at the possibility of undiscovered particles or even a new "fifth force" beyond the four known fundamental forces.

From Science Daily ● May 19, 2026

The next key objective is to determine whether a subtle fifth force truly affects it.

From Science Daily ● Nov. 16, 2025

As well as believing that they may find a new, fifth force of nature, researchers hope to find evidence of an invisible substance that makes up most of the Universe called Dark Matter.

From BBC ● Apr. 22, 2022

Many had hoped, and some had expected, the most powerful particle accelerator to have discovered dark energy, a fifth force or some other paradigm-shifting particle by now.

From BBC ● Apr. 22, 2022

From the first he got tenderness, from the second drawing, from the third color and composition, from the fourth charm, from the fifth force.

From A Text-Book of the History of Painting by Van Dyke, John Charles