Energy driving the accelerated expansion of the universe
Not to be confused with dark matter.
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In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. Assuming that the lambda-CDM model of cosmology is correct,[1] dark energy is the dominant component of the universe, contributing 68% of the total energy in the present-day observable universe while dark matter and ordinary (baryonic) matter contribute 26% and 5%, respectively, and other components such as neutrinos and photons are nearly negligible.[2][3][4][5] Dark energy's density is very low: 7×10−30 g/cm3 (6×10−10 J/m3 in mass-energy), much less than the density of ordinary matter or dark matter within galaxies. However, it dominates the universe's mass–energy content because it is uniform across space.[6][7][8]
The first observational evidence for dark energy's existence came from measurements of supernovae. Type 1A supernovae have constant luminosity, which means they can be used as accurate distance measures. Comparing this distance to the redshift (which measures the speed at which the supernova is receding) shows that the universe's expansion is accelerating.[9][10] Prior to this observation, scientists thought that the gravitational attraction of matter and energy in the universe would cause the universe's expansion to slow over time. Since the discovery of accelerating expansion, several independent lines of evidence have been discovered that support the existence of dark energy.
The exact nature of dark energy remains a mystery, and explanations abound. The main candidates are a cosmological constant[11][12] (representing a constant energy density filling space homogeneously) and scalar fields (dynamic quantities having energy densities that vary in time and space) such as quintessence or moduli. A cosmological constant would remain constant across time and space, while scalar fields can vary. Yet other possibilities are interacting dark energy, an observational effect, and cosmological coupling (see the Theories of Dark Energy section).
^Idicherian Lonappan, Anto; Kumar, Sumit; R, Ruchika; Ananda Sen, Anjan (21 February 2018). "Bayesian evidences for dark energy models in light of current observational data". Physical Review D. 97 (4): 043524. arXiv:1707.00603. Bibcode:2018PhRvD..97d3524L. doi:10.1103/PhysRevD.97.043524. S2CID 119249858.
^Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; et al. (Planck Collaboration) (22 March 2013). "Planck 2013 results. I. Overview of products and scientific results – Table 9". Astronomy and Astrophysics. 571: A1. arXiv:1303.5062. Bibcode:2014A&A...571A...1P. doi:10.1051/0004-6361/201321529. S2CID 218716838.
^Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; et al. (Planck Collaboration) (31 March 2013). "Planck 2013 Results Papers". Astronomy and Astrophysics. 571: A1. arXiv:1303.5062. Bibcode:2014A&A...571A...1P. doi:10.1051/0004-6361/201321529. S2CID 218716838. Archived from the original on 23 March 2013.
^"First Planck results: the Universe is still weird and interesting". 21 March 2013. Archived from the original on 2 May 2019. Retrieved 14 June 2017.
^Sean Carroll, Ph.D., Caltech, 2007, The Teaching Company, Dark Matter, Dark Energy: The Dark Side of the Universe, Guidebook Part 2. p. 46. Retrieved 7 October 2013, "...dark energy: A smooth, persistent component of invisible energy, thought to make up about 70 percent of the current energy density of the universe. Dark energy is known to be smooth because it doesn't accumulate preferentially in galaxies and clusters..."
^Steinhardt, Paul J.; Turok, Neil (2006). "Why the cosmological constant is small and positive". Science. 312 (5777): 1180–1183. arXiv:astro-ph/0605173. Bibcode:2006Sci...312.1180S. doi:10.1126/science.1126231. PMID 16675662. S2CID 14178620.
^"Dark Energy". Hyperphysics. Archived from the original on 27 May 2013. Retrieved 4 January 2014.
^Ferris, Timothy (January 2015). "Dark Matter(Dark Energy)". National Geographic Magazine. Archived from the original on 10 June 2015. Retrieved 10 June 2015.
^Overbye, Dennis (20 February 2017). "Cosmos Controversy: The Universe Is Expanding, but How Fast?". The New York Times. Archived from the original on 4 April 2019. Retrieved 21 February 2017.
^Peebles, P. J. E.; Ratra, Bharat (2003). "The cosmological constant and dark energy". Reviews of Modern Physics. 75 (2). American Physical Society: 559–606. arXiv:astro-ph/0207347. Bibcode:2003RvMP...75..559P. doi:10.1103/RevModPhys.75.559. S2CID 118961123.
^Cookson, Clive (3 June 2011). "Moon findings muddy the water". Financial Times. Archived from the original on 22 November 2016. Retrieved 21 November 2016.
^Carroll, Sean (2001). "The cosmological constant". Living Reviews in Relativity. 4 (1): 1. arXiv:astro-ph/0004075. Bibcode:2001LRR.....4....1C. doi:10.12942/lrr-2001-1. PMC 5256042. PMID 28179856. Archived from the original on 13 October 2006. Retrieved 28 September 2006.
In physical cosmology and astronomy, darkenergy is an unknown form of energy that affects the universe on the largest scales. Its primary effect is to...
the mass–energy content of the universe is 5% ordinary matter, 26.8% dark matter, and 68.2% a form of energy known as darkenergy. Thus, dark matter constitutes...
and energy in the universe is darkenergy which is responsible for the acceleration of the expansion of the universe, and about 25.8%±1.1% is dark matter...
accelerating, an observation attributed to an unexplained phenomenon known as darkenergy. The Big Bang models offer a comprehensive explanation for a broad range...
BAO measurements help cosmologists understand more about the nature of darkenergy (which causes the accelerating expansion of the universe) by constraining...
The DarkEnergy Survey (DES) is an astronomical survey designed to constrain the properties of darkenergy. It uses images taken in the near-ultraviolet...
The Joint DarkEnergy Mission (JDEM) was an Einstein probe that planned to focus on investigating darkenergy. JDEM was a partnership between NASA and...
The DarkEnergy Spectroscopic Instrument (DESI) is a scientific research instrument for conducting spectrographic astronomical surveys of distant galaxies...
darkenergy. Darkenergy is now believed to be the single largest component of the universe, as it constitutes about 68.3% of the entire mass–energy of...
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This model requires the universe to contain large amounts of dark matter and darkenergy whose nature is currently not well understood, but the model...
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light. The expansion rate appears to be accelerating owing to darkenergy. Assuming darkenergy remains constant (an unchanging cosmological constant) so...
and is still doing so. Physicists have postulated the existence of darkenergy, appearing as a cosmological constant in the simplest gravitational models...
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model, there are important components of Ω due to baryons, cold dark matter and darkenergy. The spatial geometry of the universe has been measured by the...
model of 2007 assumes an exotic form of darkenergy called phantom energy, which possesses negative kinetic energy and would usually cause the universe to...
Most of the remaining mass-energy in the observable universe is made up of an unknown form, dubbed dark matter and darkenergy. Outer space does not begin...