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

While dark matter is invisible and difficult to detect, it may still follow these familiar laws or possibly be influenced by a fifth force that scientists have not yet identified.

From Science Daily • Nov. 16, 2025

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

From Science Daily • Nov. 16, 2025

That is because a fifth force and any particles associated with it are not part of the Standard Model of particle physics.

From BBC • Aug. 10, 2023

They build on results announced in 2021 in which the Fermilab team first suggested the possibility of a fifth force of nature.

From BBC • Aug. 10, 2023

But there was more trouble still with the fifth force, the Indians, who were under their own chiefs.

From The Passing of New France : a Chronicle of Montcalm by Langton, H. H. (Hugh Hornby)