equivalence principle

American  

noun

Physics.

1. (in relativity) the principle that, in any small region of space-time, the effects of a gravitational field are indistinguishable from those of an appropriate acceleration of the frame of reference.

---

equivalence principle Scientific  

/ ĭ-kwĭv′ə-ləns /

1. A principle central to General Relativity stating that a gravitational field is locally indistinguishable from the effects of inertial forces. For example, according to the equivalence principle, it is impossible for someone in a box who experiences a force pushing him to the bottom of the box to know, from the force alone, whether that force is the result of a gravitational field (the box is standing on the surface of a planet) or an acceleration (the box is being pushed by a rocket).

---

Etymology

Origin of equivalence principle

First recorded in 1915–20

Example Sentences

See Examples For:

equivalence principle

The equivalence principle says that gravity should effectively vanish locally for an observer in free fall.

From Science Daily ● Sep. 8, 2026

Until now, however, nobody had tested whether the equivalence principle holds for matter and antimatter.

From Science Magazine ● Sep. 27, 2023

But for the Unruh effect, it’s a matter of acceleration—which is, per Einstein’s equivalence principle, gravity’s mathematical equal.

From Scientific American ● May 20, 2022

Analyses of these data7,8 have verified the strong equivalence principle, by showing that the accelerations of the two bodies towards the Sun differ by no more than a few parts per 1013.

From Nature ● Jul. 3, 2018

This idea that free fall is indistinguishable from, and hence equivalent to, zero gravity is called the equivalence principle.

From Textbooks ● Oct. 13, 2016