Related topics: galaxies , hubble space telescope , universe , dark matter , gravity
Dark energy
hideIn physical cosmology and astronomy, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark energy is the most popular way to explain recent observations that the universe appears to be expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 74% of the total mass-energy of the universe.
Two proposed forms for dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant is physically equivalent to vacuum energy. Scalar fields which do change in space can be difficult to distinguish from a cosmological constant because the change may be extremely slow.
High-precision measurements of the expansion of the universe are required to understand how the expansion rate changes over time. In general relativity, the evolution of the expansion rate is parameterized by the cosmological equation of state. Measuring the equation of state of dark energy is one of the biggest efforts in observational cosmology today.
Adding the cosmological constant to cosmology's standard FLRW metric leads to the Lambda-CDM model, which has been referred to as the "standard model" of cosmology because of its precise agreement with observations. Dark energy has been used as a crucial ingredient in a recent attempt to formulate a cyclic model for the universe.
For more information about Dark energy, read the full article at
Wikipedia.
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News tagged with dark energy
Dark Energy v. The Void: What if Copernicus was Wrong?
Sep 26, 2008 |
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Dark energy is at the heart of one of the greatest mysteries of modern physics, but it may be nothing more than an illusion, according physicists at Oxford University. The problem facing astrophysicists is that they have ...
Can R2 gravity explain dark matter?
Apr 20, 2009 |
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(PhysOrg.com) -- "In many ways, the standard model of cosmology works very well," Jose Cembranos tells PhysOrg. "However, there are very basic features that we just do not know. We have dark energy and dark matter. They d ...
XMM-Newton's massive discovery
Aug 25, 2008 |
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(PhysOrg.com) -- ESA's orbiting X-ray observatory XMM-Newton has discovered the most massive cluster of galaxies seen in the distant Universe until now. The galaxy cluster is so big that there can only be ...
Tackling the big questions -- approaching a revolution in our understanding of gravity
Nov 05, 2008 |
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(PhysOrg.com) -- The way galaxies move through the cosmos has recently begun to baffle scientists. Even when the gravitational theories of Newton and Einstein are taken into account, the universe is expanding and galaxies ...
Voiding the Cosmic Void: We're not at Center of the Universe After All
Dec 10, 2008 |
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Models of the universe that place us near the center of a large, sparse region don't jibe with astronomical observations. Cosmologists at the University of British Columbia reached the conclusion through a new analysis that ...
Dark Energy From the Ground Up: Make Way for BigBOSS
Aug 07, 2009 |
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(PhysOrg.com) -- Several ways have been proposed to examine dark energy, in hopes of finding out just what it is. One of them, "supernovae" for short, certainly works: it's how dark energy was discovered in ...
Dark Energy Found Stifling Growth in Universe
Dec 16, 2008 |
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(PhysOrg.com) -- For the first time, astronomers have clearly seen the effects of "dark energy" on the most massive collapsed objects in the universe using NASA's Chandra X-ray Observatory. By tracking how ...
A Theory of Dark Matter
Sep 08, 2009 |
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Among the most astounding, unexpected, and important achievements of the past century (or even more) have been the discoveries of dark matter and dark energy, collectively dubbed the "dark sector."
New Data Suggests We Don’t Live in a Void, and Supports Dark Energy
Jan 28, 2009 |
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(PhysOrg.com) -- An alternative proposal to dark energy in which the Earth sits near the center of a large void is undergoing scrutiny, and the results show that void models fit poorly with observed data. ...
The great cosmic challenge
Oct 28, 2008 |
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(PhysOrg.com) -- Today cosmologists are challenging the world to solve a compelling statistical problem, to bring us closer to understanding the nature of dark matter and energy which makes up 95 per cent of the ‘missing’ ...
Galactic nuclei offer some indication of axionlike particles
May 28, 2009 |
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(PhysOrg.com) -- “Axionlike particles are interesting because they come up regularly when scientists study string theory. By looking at their properties, you hope to learn about string theory, or some other unified theory ...
Refined Hubble Constant narrows explanations for dark energy
May 07, 2009 |
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Whatever dark energy is, explanations for it have less wiggle room following a Hubble Space Telescope observation that has refined the measurement of the universe's present expansion rate to a precision where ...
Aussie galaxy survey to lead to 'new physics'
Dec 08, 2009 |
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(PhysOrg.com) -- Australian astronomers have released the first set of data from the first project to look at the effects of "dark energy" halfway back in the Universe's lifetime.
The day the universe froze: New dark energy model includes cosmological phase transition
May 08, 2009 |
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Imagine a time when the entire universe froze. According to a new model for dark energy, that is essentially what happened about 11.5 billion years ago, when the universe was a quarter of the size it is today.
Variability of type 1a supernovae has implications for dark energy studies
Aug 12, 2009 |
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(PhysOrg.com) -- The stellar explosions known as type 1a supernovae have long been used as "standard candles," their uniform brightness giving astronomers a way to measure cosmic distances and the expansion ...
