Dark Energy Confirmed By Australian WiggleZ Sky Scan

Phoghat writes "An Australian team of researchers scanned the sky using WiggleZ Dark Energy survey and found confirming evidence of Dark Energy. Einstein is correct, as so far, usual." Meanwhile, the International Space Station is looking for dark *matter* .

Comments

Bad pop-sci writing makes kittens sad

[Sneftel]

here is the actual press release, which (unlike that article) doesn't skip over what they actually did.

Re:Bad pop-sci writing makes kittens sad

[Dachannien]

The press release is almost as bad, providing only one paragraph that actually mentions in extremely general terms what they did (something about observing galaxy and cluster distributions).

Also, the distinction not made here is that confirming the accelerating expansion of the universe is not the same thing as confirming the existence of dark energy. (And that's aside from "supporting evidence" not being the same as "confirming evidence".) There may be some other phenomenon at work here (e.g., something occurring off-brane and affecting our universe from outside, if the brane world theory turns out to be right), and observations of the structure of matter in the universe may not be sufficient to distinguish between dark energy and other possible phenomena.

Re:Bad pop-sci writing makes kittens sad

[Nadaka]

That is exactly what dark energy is. Something that causes the universe to expand, but we really don't know what it is. It doesn't matter what specifically is, it is still called dark energy. Just like we have no idea what dark matter is, but it almost certainly exists.

Re:Bad pop-sci writing makes kittens sad

[Artifakt]

If you use the term 'Dark Energy' for a place-holder of sorts, as many people popularising the concept still do, you're right, but the term has become more than that (which I guess leaves you semi-right) :-)

There are basically three, maybe four classes of hypothesis about dark energy.
1. There's an original set of hypothesis that was based on some estimates about the amount of normal matter in the universe and the amount of dark matter and dark energy there would need to be to make the universe just barely closed, based on the raw data astronomers had about 1994-95.
2. There's a second set of them, based on more current data, circa 2005-10. These are based on their being a lot more visible mass in the universe than we once thought in the 90's, but still a lot less (an order of magnitude, at the very least) than needed to close the universe. .They're also based on being able to rule out both some forms of undetected normal matter and possible types of dark matter. So we have some idea of what dark matter is, in that we now are sure it doesn't behave like most of those earlier models. In particular, we now are pretty sure dark matter doesn't pack together in the same way as normal matter - it won't 'schrunch down' to make something as compact as a star or a galaxy, but instead has a much shallower density gradient, forming huge clouds that are not much denser in their middles than near the edges. Unfortunately, almost none of the data seems to predict that dark matter is any of the hypothetical particles from various theories that seem likely in particle physics/quantum mechanics/string theory. Maybe it's a mixture of several, but that's a complex explanation and physicists are reluctant to go with that.
3. Maybe there's a simple explanation, one that requires only a single type of dark matter and a single force for dark energy..Maybe there's even a single theory.that will tie both of them together. But all the types of hypothesis considered for that role are in the area of far from mainstream physics. They all have a certain flakey side to them, almost like the electric universe hypothesis. (And no, I'm not saying that electric universe is a valid contender for a theory to explain dark energy - it does not appear to be at all - I'm just saying that the third group of hypothesis are every bit as strange as E.U.).
4. There's the occasional really weird hypothesis, that doesn't even worry about whether it predicts the universe is flat, doesn't seem to support a simple, single form of dark matter either, and is basically baroque in its elaboration, quirky in its math, and filled with ad-hoc assumptions where we are hoping that instead we will be able to derive some of the fundamental constants from simpler basics..There's a lack of elegant symmetry to the maths, and a certain amount of 'just because' to the underlying concepts. These models look like long-shots to most of the physics community, but if one of them gains traction, we would need to quit worrying about the relative flatness of the universe and why it might be expanding - for many of these models, expansion now doesn't necessarily mean the universe ever had an actual big bang, or an initial inflationary period either, and you can probably relax about the big rip too.

WTF Grammar

[degeneratemonkey]

Last part of summary segfaults my internal parser.

Re:WTF Grammar

[TheLink]

That confirms the existence of dark grammar.

A bit of a stretch...

[Eggplant Jeff]

Seems like TFA is slightly misleading though. They didn't confirm DARK ENERGY, they provided a bunch of data that confirms the universe is expanding AS EXPECTED PER CURRENT THEORY (and current theory uses dark energy to explain). It isn't like they built a dark energy detector and said "Wow, the readings are off the charts!"

Re:A bit of a stretch...

[mangu]

They didn't confirm DARK ENERGY, they provided a bunch of data that confirms the universe is expanding AS EXPECTED PER CURRENT THEORY (and current theory uses dark energy to explain).

You inverted cause and effect. There's no theory for the expansion of the universe by itself, dark energy is a theory that was created to explain the *measured* expansion. The problem with it is that it's ad hoc, dark energy is not predicted by any other effect that we have observed.

The press release was skimpy on details, but if I got it right it has demonstrated that dark energy is a good fit to the observed distribution of visible mass in the universe.

Re:Educational Songs

[drinkypoo]

When I was a kid, TV shows had songs about the alphabet and counting. Apparently, The Wiggles are doing children's edutainment about theoretical physics? Wow...

The cat in the box goes 'round and 'round...
Round and round
Round and round
The cat in the box goes 'round and 'round...
Now let's see if it's dead!

Cosmological Constant

[bill_mcgonigle]

WTF has Einstein to do with this?!

I assume TFS was referring to the cosmological constant - some have figured that Dark Energy is the mechanism behind the lambda* in Einstein's equations.

*someday Unicode will work on Slashdot...

More Accurate Description

[Lluc]

A team of Australian researchers has observed 200,000 galaxies, confirming existing theories about the expansion of the universe. These theories require an unobserved force known as dark energy to account for the expansion of the universe versus contraction that is predicted due to gravitational forces. Dark energy and dark matter have not yet been observed or measured in any way.

Re:Einstein was right?

[bunratty]

Yes. The reason that it was a mistake is that relativity predicts that the universe must be contracting or expanding. Because Einstein thought that the universe was static, instead of actually making the prediction, he added a fudge factor of gravitation repulsion that would keep the universe from collapsing under its own gravity. So he was wrong, because the universe is in fact expanding.

The reason it was the biggest mistake of his life is that adding gravitational repulsion to gravity produces an unstable equilibrium, so it would not have resulted in a steady state even if he was right. All matter would have had to have been equally distributed across the universe, and any perturbation would have caused local clumps that would collapse under gravity. So he incorrectly added his incorrect fudge factor. He was very, very wrong.

There's a reason he called it his biggest mistake. He made an obviously wrong prediction instead of correctly predicting the expansion of the universe. The fact that we now detect a repulsive force has nothing to do with Einstein's prediction except that it's also a repulsive force. It's just coincidence.