Is Dark Energy the Cause of the Universe's Accelerating Expansion?

[phy_freak]

What do they mean by this: "Albert Einstein's concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances."

I found it here: http://www.jpl.nasa.gov/news/news.cfm?release=2011-149
in the second paragraph.

could anyone explain this with examples, if possible, please thanks!

 

[HallsofIvy]

They state that this is an alternate theory, different from Einstein's theory of gravity from general relativity. And notice that, in the sentence just before, they state that the evidence gained contradicts that alternate theory.

 

[Naty1]

Your question is really about cosmological expansion caused by negative pressure...not GRAVITY...traditional gravity is a separate entity. Empty space has no gravity, but does have negative pressure!

The paper also says this:

The findings offer new support for the favored theory [meaning Einstein's general thweory] of how dark energy works -- as a constant force, uniformly affecting the universe and propelling its runaway expansion... "The results tell us that dark energy is a cosmological constant, as Einstein proposed. If [regular,typical] gravity were the culprit, then we wouldn't be seeing these constant effects of dark energy throughout time."

So what is being said is that the force IS in accord with Einstein's concept of a cosmological 'constant' and the force is 'constant' as Einstein proposed.

Wikipedia explains:

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

Nature

The nature of this dark energy is a matter of speculation. The evidence for dark energy is only indirect...

Independently from its actual nature, dark energy would need to have a strong negative pressure (acting repulsively) in order to explain the observed acceleration in the expansion rate of the universe.

According to General Relativity, the [positive] pressure within a substance contributes to its gravitational attraction for other things just as its mass density does. ...
[negative pressure is repulsive]

This accelerating expansion effect is sometimes labeled "gravitational repulsion", which is a colorful but possibly confusing expression. In fact a negative pressure does not influence the gravitational interaction between masses—which remains attractive—but rather alters the overall evolution of the universe at the cosmological scale, typically resulting in the accelerating expansion of the universe despite the attraction among the masses present in the universe...