dark energy

(redirected from Negative gravity)
Also found in: Dictionary.

dark energy,

repulsive force that opposes the self-attraction of matter (see gravitationgravitation,
the attractive force existing between any two particles of matter. The Law of Universal Gravitation

Since the gravitational force is experienced by all matter in the universe, from the largest galaxies down to the smallest particles, it is often called
..... Click the link for more information.
) and causes the expansion of the universe to accelerate. The search for dark energy was triggered by the discovery (1998) in images from the Hubble Space TelescopeHubble Space Telescope
(HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe from a position some 350 mi (560 km)
..... Click the link for more information.
 of a distant supernova that implied an accelerating, expanding universe, which in turn required a new cosmological model (see cosmologycosmology,
area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe. Modern Cosmological Theories
..... Click the link for more information.
). Although dark energy is predicted in particle physics, it has never been directly observed. It is generally agreed, however, that dark energy dominates the universe, which is estimated to have a composition of about 68–70% dark energy, 26–27% dark matterdark matter,
material that is believed to make up nearly 27% of the mass of the universe but is not readily visible because it neither emits nor reflects electromagnetic radiation, such as light or radio signals.
..... Click the link for more information.
, and 4–5% normal visible matter such as stars. By 2006, astronomers using the space telescope to examine more distant supernovas had found evidence of the effects of dark energy dating to 9 billion years ago. Observations with the Chandra X-ray Observatory, published in 2008, indicate that dark energy is also retarding the growth of distant galaxy clusters.

The concept of dark energy was first proposed, and then discarded, by Albert Einstein early in the 20th cent. His theory of general relativityrelativity,
physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.
..... Click the link for more information.
 implied that the pull of gravity would make the universe collapse, but, like many scientists of his time, he assumed the universe to be static and unchanging. To make his equations fit these assumptions, Einstein added a "cosmological constant" whose effect was repulsive. When American astronomer Edwin HubbleHubble, Edwin Powell,
1889–1953, American astronomer, b. Marshfield, Mo. He did research (1914–17) at Yerkes Observatory, and joined (1919) the staff of Mt. Wilson Observatory, Pasadena, Calif., of which he became director. Building on V. M.
..... Click the link for more information.
 discovered that the universe was expanding, it was assumed that the universe must be slowing down because of gravity and might even come to a halt. This led Einstein to remove the cosmological constant from his equations and to say that it had been the biggest blunder of his career.

dark energy

The energy associated with the acceleration of the expansion of the Universe. About three-quarters of the energy of the Universe exists in the form of dark energy. The existence of dark energy can be taken into account using a nonzero value for the cosmological constant but the nature of this energy is not understood at the present time.
References in periodicals archive ?
This contrasts with the hypothesis by Song & Simons (2003) who interpreted a correlation between negative gravity anomalies and seismic asperities.
This radiation, traveling like a plane wave above the disc, acts on other bodies like a negative gravity.
In a context of motivational gravity, each of these big five could--on a priori conceptual and theoretical grounds alone--either enhance or reduce tolerance thresholds for negative gravity.
In SSW Estonia, the negative gravity effect of the thick crust should be much stronger, but here it is compensated by the high-density granulite facies blocks in the upper crust which, together with the uplifted blocks of the lower crust, give even positive anomalies.
The low-density othogneisses of the Keprnik Unit cause negative gravity anomaly on south near Sumperk (G8).
I read in the International Herald Tribune that Einstein's theories about negative gravity are just now being verified by teams of physicists.
Stockton wrote one of the earliest science-fiction stories, A Tale of Negative Gravity (Century Magazine, December 1884).
Fishbach's fifth force is a kind of negative gravity, a component of gravity that is repulsive for ordinary matter and that depends on the nature of the substances involved, as ordinary gravity does not.
The Tourbillon, with its fascinating mechanical construction, eliminating the negative gravity influence on accuracy, is considered the Masterpiece of watch making, only found in the highest end brands, incorporated in watches selling at US$ 50,000 and more.
The speed of its rotation is so high at the equator that it experiences negative gravity.
It's the tallest ride in Orlando and features a non-inverted loop and negative gravity spiral, both world-firsts for coasters.
Jonathan's previous play, The Pull of Negative Gravity, won an Edinburgh Fringe First for innovation and outstanding new writing before transferring to New York.