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

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Example Sentences

See Examples For:

fifth force

"That would indeed be surprising, and, in addition to other theories, it could point to the existence of a fifth force," as Soter outlines.

From Science Daily ● Sep. 18, 2026

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

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

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 John Charles Van Dyke

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