Dark Energy

Dark Energy should not to be confused with Dark Matter or Dark Fluid.

In physical cosmology and astronomy, dark energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate.

Assuming that the standard model of cosmology is correct, the best current measurements indicate that dark energy contributes 68% of the total energy in the present-day observable universe. The mass-energy of dark matter and ordinary (baryonic) matter contribute 27% and 5%, respectively, and other components such as neutrinos and photons contribute a very small amount. The density of dark energy is very low much less than the density of ordinary matter or dark matter within galaxies. However, it dominates the mass–energy of the universe because it is uniform across space.

Two proposed forms for dark energy are the cosmological constant, representing 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 can be formulated to be equivalent to the zero-point radiation of space i.e. the vacuum energy.Scalar fields that change in space can be difficult to distinguish from a cosmological constant because the change may be extremely slow. Read more

In the News ...

Euclid space telescope: The groundbreaking mission to study dark matter and dark energy   Live Science - July 6, 2023

The Euclid space telescope uses its incredibly wide field of view to hunt for two of the universe's most mysterious components: dark matter and dark energy.

Supernova Explosions Reveal Precise Details of Dark Energy and Dark Matter   SciTech Daily - October 26, 2022

An analysis of more than two decades’ worth of supernova explosions convincingly boosts modern cosmological theories and reinvigorates efforts to answer fundamental questions. A powerful new analysis has been performed by astrophysicists that places the most precise limits ever on the composition and evolution of the universe. With this analysis, dubbed Pantheon+, cosmologists find themselves at a crossroads.

Quintessence - Dark Energy - Collapse of the Universe

The Universe is a simulation that expanded (spiraled out) at the beginning - stopping after it was created and reversing ever since. We are currently at 0,1 in the sequence - almost home.

In physics, quintessence is a hypothetical form of dark energy postulated as an explanation of the observation of an accelerating rate of expansion of the universe. Continue reading ...

Predicting how soon the universe could collapse if dark energy has quintessence  
PhysOrg - May 5, 2022

The Universe Could Collapse On Itself A Lot Quicker Than We Were Expecting  
Unilad.co.uk - May 5, 2022

The universe could stop expanding 'remarkably soon' 
Live Science - May 6, 2022

If the universe is expanding like a rubber band - when it snaps back will it collapse into itself?

'Chameleon Theory' Could Explain Why the Universe Is Blowing Up   Live Science - July 12, 2019

Can a chameleon build a galaxy? According to new computer models, yes. This isn't a surrealist joke but rather the implication of recent simulations that aim to explain the inner workings of dark energy, a mysterious force that is driving apart everything in the universe. The findings, published July 8 in the journal Nature Astronomy, lend support to a model of dark energy known as Chameleon Theory. Hints of dark energy were first discovered in the late 1990s, when cosmologists measured the light from distant supernovas and realized that the stars were dimmer than expected, suggesting that the fabric of spacetime was not only expanding, but accelerating in its expansion. Physicists proposed the existence of a force that worked in opposition to gravity, pushing things away from one another, rather than pulling them together.

Dark Energy Gets Weirder: Mysterious Force May Vary Over Time   Space.com - January 30, 2019
Dark energy is apparently even more mysterious than astronomers had thought. Scientists first proposed the existence of this invisible force two decades ago, to explain the surprising discovery that the universe's expansion is accelerating. The most-used astrophysical model of the universe's structure and evolution regards dark energy as a constant. Indeed, many astronomers believe it to be the cosmological constant, which Einstein posited in 1917 as part of his theory of general relativity. But a new study of enormous, superbright black holes known as quasars suggests that dark energy could be miscast as the cosmological constant, or any kind of constant; the force may have varied since the universe's birth 13.8 billion years ago, research team members said.

Researcher finds hint of dark energy discussion in letters between Einstein and Schrodinger   PhysOrg - December 11, 2012

Alex Harvey, a physics professor at the City University of New York has uploaded a paper in which he claims Albert Einstein and Erwin Schrodinger were writing letters suggesting the two men were on the precipice of discussing the possibility of the existence of dark energy. The letter exchange came in the years after Einstein had published his theories on general relativity, and revolved around the matter of the cosmological constant.