What is "dark energy."?

Question

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From Neil Turok article:
We also know that, in the universe today, there's something
called "dark energy." Dark energy is the energy of empty space.
I cannot understand this.
Please, before to answer, read this article.
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THE CYCLIC UNIVERSE [5.17.07]
A Talk With Neil Turok

NEIL TUROK holds the Chair of Mathematical Physics in the department of
applied mathematics and theoretical physics at Cambridge University. He
is coauthor, with Paul Steinhardt, of Endless Universe: Beyond the
Big Bang.
NEIL TUROK's Edge Bio Page
THE CYCLIC UNIVERSE
http://tech.groups.yahoo.com/group/quantum_theory/message/5255

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http://www.socratus.com

Answer 1

Energy a mystery, and is never really told what Dark Energy is.

There are very good reasons for this. The long and short of it is that Dark Energy - as conceived by our modern physicists - is a fanciful notion that would bring a Mona Lisa smile even to Einstein's lips. There is no proof that it exists, but it must exist, solely because it is universally agreed that: 1) the universe had a beginning; 2) the universe is expanding; 3) the known mass-energy of the universe cannot account for the supposed rate of expansion. Add to this that, somehow, by more recent so-called computations, this rate of expansion is accelerating, and one obtains all the ingredients for a modern scientific religion - a metaphysics of physics. Note that all of these requirements were Einstein's legacy (for all that he would have smiled!); but please remark further that, despite thousands of papers published on the subject, there is literally no experimental evidence for any of them. Hence, it is all a matter of credo quia absurdum est.

Indeed, the idea that the universe had a beginning is nothing more than an interpretation, and at that, one that is not legitimized by the First Law of Conservation of Energy. That the universe is expanding is not the result of any direct observation, but of yet another interpretation - of Redshifts and Blueshifts. And that the total measurement of mass-energy would have to account for the constraints of an interpretive model, is simply a self-validating requirement for which there can be no independent experimental proof. As for the acceleration of that expansion - well, it's all in the eyes of the beholders. All of this should have put Einstein's legacy into question. But it didn't. Instead, it produced yet another false problem: if there is not enough Matter in the universe, not enough Dark Matter, then there must be some Dark Energy.

The twists and turns of the argument are remarkable. And they indicate just how obstinate, desperate orthodoxies are - in their refusal to alter the parameters of a field of inquiry or investigation - and the extent to which they're willing to go on co-opting, patching, mending with sheer spit, models that have obviously outlived their usefulness.

Ask yourself - what would it mean to Albert Einstein to hear Dark Energy spoken of as distinct from Dark Matter or Dark Mass?? And why make the distinction when, by Dark Energy, physicists mean the most massive particle that supposedly exists? Albert undoubtedly would have exclaimed: "it's nothing more than a marketing gimmick!" And he wouldn't have been far from the truth, even if for the wrong reasons. For, indeed, according to Einstein, all energy is mass, carries mass, affects mass - and energy and mass interconvert. Mass, says Albert, is an intrinsic property of all energy. These authors happen to think he was wrong, but that is what Albert said. The mass-property of all energy was even supposed to apply to kinetic energy! - which is how DeBroglie got his Matter Waves going with a relativistic solution. There could never be Dark Energy without mass. And there could never be massless energy. Not, at least, according to Albert. Anyway, this is a minor detail, since the Dark Energy that our particle physicists talk about is only 'massless' for laughs - it was 'massless' in a distant past, but is supermassive today.

In truth, the import of uncertainty has been so abused in physics, by physicists, that they literally do not know what Dark Energy is. That is to say, they are not just uncertain about it, they are totally uncertain, ie completely confused. It's hardly surprising, then, that when they speak, they are inclined to say precisely nothing. Here, for example, is Rocky Kolb, of Fermilab, U. of Chicago:

"Recent measurements with telescopes and space probes have shown that a mysterious force-a dark energy-fills the vacuum of empty space, accelerating the universe's expansion. We don't know what dark energy is, or why it exists."
What a mysteriously tortuous presentation! The theory calls for the existence of a force (a force of expansion, as required by relativistic astrophysics); ergo an energy must exist, even if it has never been found! This is hardly surprising, of course, since particle physicists are still so ignorant of the actual physics of energy, not to mention, of massfree energy. But, apparently, to find their so-called proof of this force, we need not go very far. It suffices for them to simply point to particle theory, or quantum electrodynamics and chromodynamics, and to propose some sufficiently imposing magnitude for the energy of the so-called 'vacuum-state', and voilá the proof:
"On the other hand, particle theory tells us that, at the microscopic level, even a perfect vacuum bubbles with quantum particles that are a natural source of dark energy. But a naïve calculation of the dark energy generated from the vacuum yields a value 10120 times larger than the amount we observe. Some unknown physical process is required to eliminate most, but not all, of the vacuum energy, leaving enough left to drive the accelerating expansion of the universe. A new theory of particle physics is required to explain this physical process." (more R. Kolb)
This is not science. This is delusional self-fulfilling prophecy - a religious enterprise. One first assumes a beginning for the universe and postulates, by dint of sheer interpretation, that the universe expands. Then one assumes that sufficient quantities of Dark Matter are needed to satisfy the expansion; if there is not enough of this supposed Dark Matter, then one fills the gap with some appropriate quantity of Dark Energy and invokes the elucubrations of particle theory as supposed proof of the scientific correctness of this procedure. And then, to explain that which does not exist and to continue to chase after the elusive proof of its existence, trillions of taxpayer dollars must be consumed across the globe. If it were not the real and current state of Physics, and one prevalent worldwide, one might think it was just some lulu's idea. But maybe it is.
In the impoverished sense, therefore, in which Dark Energy is spoken about in the modern academia, there is no Dark Energy at all. It's a fiction. So it's hardly surprising no one knows what it is.

However, even though, after traversing the tortuous labyrinth of an "argument" such as Kolb's, one cannot but conclude that its subject is a fiction, a nothing - in need of never ending new fictions to prop it up - one is nevertheless told that it's a 'discovery'! Though it's unknown what Dark Energy is, the very need to have it, somehow, constitutes a discovery!:

"The dramatic discovery of dark energy showed that empty space is filled with a mysterious energy that increases as the universe expands."
And now there is space for every conceivable sort of mysticism and every demented idea of exotic bombs. Mass-energy could be converting into dark electromagnetic energy, and that is why the universe is both running down and expanding. A way might even be found to conciliate this with the Principle of Conservation of Energy (!?). After all, the proportion of total mass-energy must vary...

Answer 2

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 currently accounts for almost three-quarters of the total mass-energy of the universe.

>>Forms of Dartk Energy:
Two proposed forms for dark energy are the
>>The dark-energy story begins in 1998, when two independent teams of astronomers were searching for distant supernovae, hoping to measure the rate at which the expansion of the universe was slowing down. They were in for a shock: the observations showed that the expansion was speeding up. In fact, the universe started to accelerate long ago, some time in the last 10 billion years
Cosmological Constant- a constant energy density filling space homogeneously.
and Quintessence= a dynamic field whose energy density can vary in time and space.
Distinguishing between the alternatives requires high-precision measurements of the expansion of the universe to understand how the speed of the expansion changes over time. The rate of expansion 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.

Answer 3

In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. [1] Assuming the existence of 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 almost three-quarters 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,[2] and quintessence, a dynamic field whose energy density can vary in time and space. Distinguishing between the alternatives requires high-precision measurements of the expansion of the universe to understand how the speed of the expansion changes over time. The rate of expansion 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.

Answer 4

In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. [1] Assuming the existence of 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 almost three-quarters 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,[2] and quintessence, a dynamic field whose energy density can vary in time and space. Distinguishing between the alternatives requires high-precision measurements of the expansion of the universe to understand how the speed of the expansion changes over time. The rate of expansion 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.

http://en.wikipedia.org/wiki/Dark_energy

Answer 5

Predictions using the General Relativity theory do not match observations concerning universal exapansion (or galactic rotation). In order to account for this, scientist propose the notion of dark energy (and dark matter). So far, there is no direct evidence of either. They are ad hoc additions used to save Einstein's theory. In other words, dark energy is the result of bad science, but it sounds really cool.