relativity
Americannoun
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the state or fact of being relative.
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Physics. a theory, formulated essentially by Albert Einstein, that all motion must be defined relative to a frame of reference and that space and time are relative rather than absolute concepts: it consists of two principal parts. The theory dealing with uniform motion special theory of relativity, or special relativity is based on the two postulates that physical laws have the same mathematical form when expressed in any inertial system, and the velocity of light is independent of the motion of its source and will have the same value when measured by observers moving with constant velocity with respect to each other. Derivable from these postulates are the conclusions that there can be no motion at a speed greater than that of light in a vacuum, mass increases as velocity increases, mass and energy are equivalent, and time is dependent on the relative motion of an observer measuring the time. The theory dealing with gravity general theory of relativity, or general relativity is based on the postulate that the local effects of a gravitational field and of acceleration of an inertial system are identical.
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dependence of a mental state or process upon the nature of the human mind.
relativity of values; relativity of knowledge.
noun
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either of two theories developed by Albert Einstein, the special theory of relativity , which requires that the laws of physics shall be the same as seen by any two different observers in uniform relative motion, and the general theory of relativity which considers observers with relative acceleration and leads to a theory of gravitation
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philosophy dependence upon some variable factor such as the psychological, social, or environmental context See relativism
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the state or quality of being relative
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Either of two theories in physics developed by Albert Einstein, General Relativity or Special Relativity.
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See Notes at Einstein gravity space-time
Closer Look
Albert Einstein's two theories of relativity were the first successful revisions of Newtonian mechanics—a mechanics so simple and intuitive that it was held to be a permanent fixture of physics. Uniting the theories is the idea that two observers traveling relative to each other may have different perceptions of time and space, yet the laws of nature are still uniform, and certain properties always remain invariant. Einstein developed the first theory, the theory of Special Relativity (1905), to explain and extend certain consequences of Maxwell's equations describing electromagnetism, in particular, addressing a puzzle surrounding the speed of light in a vacuum, which was predicted always to be the same, whether the light source is stationary or moving. Special Relativity considers the laws of nature from the point of view of frames of reference upon which no forces are acting, and describes the way time, distance, mass, and energy must be perceived by observers who are in uniform motion relative to each other if the speed of light must always turn out the same for all observers. Two implications of Special Relativity are space and time dilation. As speed increases, space is compressed in the direction of the motion, and time slows down. A famous example is the space traveler who returns to Earth younger than his Earth-dwelling twin, his biological processes proceeding more slowly due to his relative speed. These effects are very small at the speeds we normally experience but become significant at speeds approaching the speed of light (known as relativistic speeds). Perhaps the best-known implication of Special Relativity is the equation E=mc2, which expresses a close relation between energy and mass. The speed of light is a large number (about 300,000 km per second, or 186,000 mi per second), so the equation suggests that even small amounts of mass can be converted into enormous amounts of energy, a fact exploited by atomic power and weaponry. Einstein's General Theory of relativity extended his Special Theory to include non-inertial reference frames, frames acted on by forces and undergoing acceleration, as in cases involving gravity. The General Theory revolutionized the way gravity, too, was understood. Since Einstein, gravity is seen as a curvature in space-time itself.
Other Word Forms
- nonrelativity noun
Etymology
Origin of relativity
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
From a cosmological perspective, they can use Albert Einstein's equations of general relativity to calculate how much energy is needed to explain the fact that the universe is expanding at an accelerated rate.
From Scientific American
According to Einstein’s special theory of relativity, time’s flow depends on how fast you’re moving.
From Scientific American
One reason is that it seems to conflict with one of our other theories, general relativity, used to describe gravity.
From Scientific American
This year’s eclipse took place almost exactly a century after the 1922 solar eclipse in Australia that provided scientists the opportunity to confirm the “proof” of Albert Einstein’s general theory of relativity.
From New York Times
Dr. Gopnik compared the theory of mind of large language models to her own understanding of general relativity.
From New York Times
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
