====== Dark Energy ======

>The observational results of the latest 15 to 20 years have established a standard model for the cosmology which has some amazing consequences. A mysterious entity, the dark energy, has been confirmed as the dominant component of the Universe, and is also responsible for its accelerated expansion. __However, its physical nature remains unknown. Unveiling the nature of the dark energy is one of the main problems of cosmology."__\\ \\ //Source :// [[http://www.sciencedirect.com/science/article/pii/S2405601415005313|The Dark Energy Survey: Status and First results]] {{:oa_padlock_grn.png?16&nolink|open access}}//Nuclear and Particle Physics Proceedings// Volumes 273–275, April–June 2016, Pages 302–308, 37th International Conference on High Energy Physics (ICHEP)

Dark Energy is currently believed to make up 68.3% of the universe, and is the most accepted hypothesis to explain various observations (beginning in the 1990s) indicating that the [[https://en.wikipedia.org/wiki/Hubble%27s_law|universe is expanding]] //at an accelerating rate//.

Note that the speed at which it's expanding has not yet been determined to an acceptable degree of accuracy - with different observation techniques apparently showing widely differing rates.

[[https://en.wikipedia.org/wiki/Dark_energy#Theories_of_dark_energy|Theories of Dark Energy]] include:

  * As a form of the Cosmological Constant (see link below)
  * A result of Modified Gravity
  * Quintessence - a newly proposed dynamical field
  * As a result of Time Variations by observers  etc

Currently, none of the proposed theories has enough evidence to be accepted by all theorists.

//Note:// Unlike [[content:physics:cosmology:dark_matter|Dark Matter]], which many comologists believe exists in so-called 'halos' around galaxies, Dark Energy would necessarily pervade every part of the entire universe -// but no effects have ever been detected in any experiments on Earth, or in our 'local' space research. //The calculated 'push' of dark energy, however, is very low :

>The amount of dark energy contained in the volume of the entire Earth is about as much as the amount of electricity used by the average US citizen every year [...]"\\ \\ Source : [[https://yalebooks.yale.edu/book/9780300218275/138|' 13.8 ']] by Dr. John Gribbin, pp. 210-211

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Also see [[content/physics/cosmology/cosmological_constant]]

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