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 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

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

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

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

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 H. H. (Hugh Hornby) Langton