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
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.
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 ...
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. ...
Ticking stellar time bomb identified (w/ Video)
Nov 17, 2009 |
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(PhysOrg.com) -- "One of the major problems in modern astrophysics is the fact that we still do not know exactly what kinds of stellar system explode as a Type Ia supernova," says Patrick Woudt, from the University ...
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 ...
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."
Precise picture of early Universe supports 'dark matter' theory
Nov 02, 2009 |
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A detailed picture of the seeds of structures in the universe has been unveiled by an international team co-led by a Cardiff University scientist.
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 ...
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 ...
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 ...
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.
Hunting for Planets in the Dark
Nov 19, 2009 |
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A proposed space mission that aims to measure dark energy could also detect planets that current surveys are unable to find.
Do we need dark matter?
Nov 12, 2009 |
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It's the biggest problem in physics: the matter we can see in the universe accounts for just five per cent of the observed gravity that holds galaxies together.
Refurbished Hubble Ready to Resume Exploration
Space & Earth / Space Exploration
May 19, 2009 |
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(PhysOrg.com) -- The Hubble Space Telescope has been with us for nearly two decades. In that time, its breathtaking images have captured people’s imaginations and its groundbreaking science has revealed some ...
Better Supernovae Measurements Aim To Improve Understanding of Dark Energy
May 22, 2009 |
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(PhysOrg.com) -- A new technique for measuring the distances to supernovae more accurately than ever before has been developed by a team of scientists from Yale University, Lawrence Berkeley National Laboratory ...
