fifth force

American  

noun

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

---

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)

---

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.

---

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

"If dark matter is not subject to a fifth force, then galaxies -- which are mostly made of dark matter -- will fall into these wells like ordinary matter, governed solely by gravity. On the other hand, if a fifth force acts on dark matter, it will influence the motion of galaxies, which would then fall into the wells differently. By comparing the depth of the wells with the galaxies' velocities, we can therefore test for the presence of such a force."

From Science Daily

"At this stage, however, these conclusions do not yet rule out the presence of an unknown force. But if such a fifth force exists, it cannot exceed 7% of the strength of gravity -- otherwise it would already have appeared in our analyses," says Nastassia Grimm first author of the study and former postdoctoral researcher at the Department of Theoretical Physics at UNIGE's Faculty of Science who has recently joined the Institute of Cosmology and Gravitation at the University of Portsmouth.

From Science Daily

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

From Science Daily

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

From BBC