Necessity of Dark Energy Questioned

ttnuagmada points us to an article about scientist David Wiltshire's suggestion that theorized dark energy is not needed to describe the expansion of the universe. His work challenges assumptions made about the distribution of matter in the universe. Early solutions to general relativity were based on a "smooth distribution" of matter. Wiltshire's approach focuses on a "lumpy" dispersal, which more accurately fits data from modern studies. We have discussed other theories about dark energy in the past. Quoting: "Through observational projects like the Sloan Digital Sky Survey and the 2 Degree Field survey, we now have a much better picture of the large-scale structure of the universe and we know that galaxies are not uniformly distributed. 'Rather, they are in clusters sprinkled thinly in filaments and "bubble walls" surrounding huge voids hundreds of millions of light-years across,' Wiltshire says.

Comments

Skeptical

[Black Parrot]

Mostly because of this:

we now have a much better picture of the large-scale structure of the universe and we know that galaxies are not uniformly distributed. 'Rather, they are in clusters sprinkled thinly in filaments and "bubble walls" surrounding huge voids hundreds of millions of light-years across,' which we have already known for decades. He seems to think all the cosmologists who have signed on with the dark energy model are unaware of it.

Re:Skeptical

[sam_handelman]

Just because you know that something is happening doesn't mean that you account for it correctly or fully appreciate the implications; I'm a biologist, all the systems I deal with are heterogeneous, and it's always a major bitch to deal with. That said, I share your skepticism but this doesn't strike me as implausible - although I know essentially nothing about astrophysics.

Re:Skeptical

[Bill, Shooter of Bul]

From the article, it seems like he believes that this lumpiness was always there, rather than an earlier smooth distribution they've been assuming.

While we might not ever know who is correct in this regard, I tend to prefer theories that don't have the need for dark energies, or matter,even if that really really screws up the equations we use to model the early universe. I think at some point every physicist just stares at a black board somewhere and says to himself " thats fucked up". We really have lost the elegance of the universe being a series of spherical shells rotating around the earth. Since that point we've managed to go through cycles of discovering elegance in the universe on a deeper level (the simple math of kepplar and Newton), and having to reject it for more complexity( Einstien's huge matrix of PDE's ). Let this be a lesson to us all, Don't let what should be prevent you from seeing what is.

Re:Skeptical

[bigpicture]

Exactly, even though we don't need to postulate the presence of "Dark Matter" to construct mathematical models of the expanding Universe, Einstein did not need the "ether" theory to construct "relativity" mathematical models that incorporated how light seems to behave.

Still that does not prove that the "ether" either exists or doesn't exist. Just that it is not necessary to incorporate into a mathematical model, that will more or less express what is observed. But we still have the question of "zero point energy", what exactly is it? And what possible connections or similarities might it have with "dark matter" and "ether" theories.

I have my own theory, and it is about the limitations of thought or of comprehension. Thought itself seems to work on a relativistic principle, where the polar opposite is always simultaneously needed as a contrast. Example: Up/Down, In/Out, Near/Far, Good/Bad etc. etc. So Einstein's theory of Relativity does not necessarily explain how the Universe works, it only explains how the limitations of thought work. Thought as a medium of awareness can therefore never grasp the Absolute, or the Non-Relativistic Totality, because that requires a different kind of awareness than thought is capable of.

Mini-Inflation events in Voids

[skeptictank]

The fact that matter forms bubbles around the voids intuitively make me think that some force is pushing matter away from the center of each void. Perhaps the center of each void is location where mini-inflation events have happened and what we see today is the reslut of these events pushing shells of matter up against each other so that they form filaments and bubbles. Just a though, IANAP though.

Re:Mini-Inflation events in Voids

[LionKimbro]

I don't think so; My understanding is that it's the force of gravity.

Here is the picture I have heard:

The universe basically, from any point, stretches out in all directions. Gravity pulls a given lump in all directions at a given time. But local things are more powerful by the law of gravity, than far things. So things start lumping with their neighbors.

Some lumpings occur earlier than other lumpings, which cause then to exert a stronger pull. These become the super-clusters (joining points between filament; such as the Virgo Cluster.)

So masses are basically pulled towards the closest super-cluster. But, ah-hah, some are pulled strongly by *two* super-clusters. These become the filament ("bubble walls.")

If you download Mitaka, you can see a lot of these things first hand, with data directly from the Sloan Digital Sky Survey.

Re:Mini-Inflation events in Voids

[John Hasler]

> Otherwise they should just sit there, riding along with the expansion of the universe as
> a whole - no?

They do, pretty much. Here is a crude, oversimplified summation:
Since there is less matter in the voids than there would be in a homogeneous universe time runs faster in them then it would in a such a universe. Therefor the universe is older seen from the voids and so they seem bigger than they should be. Meantime down here in the matter concentrations where contraction due to gravity dominates time runs slower due to all the mass than it would in a homogeneous universe. As a result contraction seems not to have progressed as it should have. Taken together these effects give the impression of a weak but all-pervading force trying to push everything apart: dark energy. When you redo the calculations taking into account the fact that the universe is older where there is less mass and younger where there is more the need to postulate dark energy vanishes.