Dark Energy

[psaturn]

Seemst to me the scientists are observing something and giving it a name to something they do NOT understand at all!!!


http://www.space.com/scienceastronom..._020115-1.html

[ QUOTE ]
Dark Energy: Astronomers Still 'Clueless' About Mystery Force Pushing Galaxies Apart

By Andrew Chaikin
Editor, Space & Science
posted: 07:00 am ET
15 January 2002

It sounds like something out of a Star Trek episode: Dark energy, a mysterious force that no one understands, is causing the universe to fly apart faster and faster. Only a few years ago, if you'd suggested something like that to astronomers, they would have told you to spend less time in front of the TV and more time in the "real" world.

But dark energy is real or at least, a growing number of astronomers think it is. No one, however, can truly explain it.

"Frankly, we just dont understand it," says Craig Hogan, an astronomer at the University of Washington at Seattle. "We know what its effects are," Hogan says, but as to the details of dark energy, "Were completely clueless about that. And everybodys clueless about it."

Dark energy entered the astronomical scene in 1998, after two groups of astronomers made a survey of exploding stars, or supernovas, in a number of distant galaxies. These researchers found that the supernovas were dimmer than they should have been, and that meant they were farther away than they should have been. The only way for that to happen, the astronomers realized, was if the expansion of the universe had sped up at some time in the past.



Until then, astronomers had generally believed that the cosmic expansion was gradually slowing down, due to the gravitational tugs that individual galaxies exert on one another. But the supernova results implied that some mysterious force was acting against the pull of gravity, causing galaxies to fly away from each other at ever greater speeds.

It was a stunning realization.

At first, other researchers questioned the result; perhaps the supernovas were dimmer because their light was being blocked by clouds of interstellar dust. Or maybe the supernovas themselves were intrinsically dimmer than scientists thought. But with careful checking, and more data, those explanations have largely been put aside, and the dark energy hypothesis has held up.

In one sense, the idea is not completely new. Einstein had included such an "anti-gravity" effect in his theory of general relativity, in his so-called cosmological constant. But Einstein himself, and later many other astronomers, came to regard this as a kind of mathematical contrivance that had little relationship to the real universe. By the 1990s no one expected that the effect would turn out to be real.

Still, anti-gravity isnt the right way to describe dark energy, says Virginia Trimble of the University of Southern California at Irvine.

"It doesnt act opposite to gravity," Trimble says. "It does exactly what general relativity says it should do, if it has negative pressure."

Trimble has a fairly simple way of imagining the phenomenon.

"If you think in terms of the universe as a very large balloon," she says, "when the balloon expands, that makes the local density of the [dark energy] smaller, and so the balloon expands some more . because it exerts negative pressure. While its inside the balloon its trying to pull the balloon back together again, and the lower the density of it there is, the less it can pull back, and the more it expands. This is what happens in the expanding universe."

The supernova evidence suggests that the acceleration kicked in about 5 billion years ago. At that time, galaxies were far enough apart that their gravity (which weakens with distance) was overwhelmed by the relatively gentle but constant repulsive force of dark energy. Since then, dark energy's continuing push has been causing the cosmic expansion to speed up, and it seems likely now that this expansion will continue indefinitely.

"It means that if you look out at the universe today, and if we wait many billions of years," says Hogan, "everything will be flying away faster and faster, and eventually well be left quite alone."

Aside from such grim forecasts, dark energy is causing quite a bit of upset for astronomers who have to adjust to an unexpected and outlandish new view of the universe. Already, they have had to accept the notion of dark matter, which is now thought to far outnumber ordinary matter in the universe, but which has never been detected in any laboratory. Now, the arrival of an unknown force that rules cosmic expansion has added insult to injury.

"I'm as big a fan of dark matter and dark energy as anybody else," says astronomer Richard Ellis of Caltech. But, he adds, "I find it very worrying that you have a universe where there are three constituents, of which only one [i.e., ordinary matter] is really physically understood."

"When you teach undergraduates, and they say, 'Well, what is dark matter?' Well, nobody's really sure. 'What is dark energy?' We're even less sure. So you have to explain to a student, that 90 percent of the universe, 95 percent, is in two ingredients that nobody really understands," says Ellis. "This isn't really progress."

No one argues that dark energy is difficult to comprehend. And as Trimble points out, it is hardly the first strange idea scientists have had to accept.

"It took two generations for people to be comfortable with quantum mechanics," she says. "The fact that you do not have good intuition about [dark energy] is true for quantum mechanics, general relativity, and lots of other things, because we cant easily mock them up in the laboratory."

And for cosmologists, dark energy has solved at least one cosmological conundrum raised by studies of the Cosmic Microwave Background, or CMB.

[/ QUOTE ]

and this is the latest article of the universe

http://www.space.com/scienceastronom...p_results.html


[ QUOTE ]
Astronomers Detect First Split-Second of the Universe
By Ker Than
Staff Writer
posted: 16 March 2006
01:59 pm ET

Scientists announced today new evidence supporting the theory that the infant universe expanded from subatomic to astronomical size in a fraction of a second after its birth.

The finding is based on new results from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001 to measure the temperature of radiant heat left over from the Big Bang, which is the theoretical beginning to the universe.

This radiation is known as the Cosmic Microwave Background (CMB), and it is the oldest light in the universe.

Using WMAP data, researchers announced in 2003 that they had pieced together a very detailed snapshot of the universe as it was about 400,000 years ago, and that they had determined things like its age, composition and development.

The previous data showed that the universe was about 13.7 billion years old. It also revealed that it wasn't until about 200 million years after the Big Bang that conditions were cool enough for the first stars to form. Scientists were also able to conclude that the universe is composed of about 4 percent real matter, about 23 percent dark matter, and about 73 percent dark energy. Nobody actually knows what dark matter or dark energy are, however.

The new WMAP observations, announced at a NASA press conference today, reveal what the universe was like in the first trillionth of a second after the Big Bang. From the microwave background, researchers teased out a new signal called the "polarization signal."

"This new signal is roughly 100 times weaker than the signal we analyzed three years ago and about a billion times less than the radiant warmth we feel from the Sun," said Lyman Page, a WMAP team member from Princeton University.

The researchers collected observations of this polarization signal to create a map of the early universe, allowing them to test a sub-theory within the Big Bang theory, called "inflation."

Inflation theory states that the universe underwent a rapid expansion immediately following the Big Bang.

"During this growth spurt, a tiny region, likely no larger than a marble, grew in a trillionth of a second to become larger than the visible universe," said WMAP researcher David Spergel, also from Princeton University.

The new observations reveal that the early expansion wasn't smooth, with some regions expanding faster than others.

"We find that density fluctuations on the 1- to 10-billion-light-year scale are larger than density fluctuations on the hundred-million-light-year scale," Spergel said. "That is just what inflation theory predicts."

These fluctuations are thought to have led to clumping of matter that allowed the formation of galaxies.

Brian Greene, a physicist from Columbia University who wasn't involved in the research, called the new findings "spectacular" and "stunning."

"A major question that people have asked for decades is where do stars and galaxies come from? The answer coming from WMAP data supports the idea that quantum fluctuations are the answer," Greene said. "WMAP's data supports the notion that galaxies are nothing but quantum mechanism writ large across the sky."

The new findings brings humanity closer to answering one of its oldest questions, that of where we come from, Greene said.

"WMAP certainly doesn't answer this question, but its data is taking us one giant step closer to the answer by giving us a precise quantitative look at the universe's earliest fraction of a second," Greene said. "It's a tiny window of time, but it's a critical one in our quest to learn what happened at time zero itself."

The new findings have been submitted to Astrophysical Journal.

[/ QUOTE ]

[Qester]

Well for the universe to be speeding up energy must be exerted, where is this energy coming from? An unknown source. For thousands of years scientists have given names to things they do not understand yet and just observations. Its like when they named the Nucleus or anything else that they just saw for the first time. Id rather they call it dark energy while figuring out what it is then "That energy which we have not named yet which is pushing the galaxies farther away" [img]/forum/images/graemlins/wink.gif[/img]

[Travail]

Wow, dark energy...this sounds scary...