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

"I've been hunting for the fifth force for as long as I've been a particle physicist," says Dr Sam Harper.

From BBC • Apr. 22, 2022

These, as yet unconfirmed results, also suggest deviations from the Standard Model, possibly as a result of an as yet undiscovered fifth force of nature at play.

From BBC • Apr. 7, 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