Dark Energy Confirmed By Australian WiggleZ Sky Scan 131
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* .
Bad pop-sci writing makes kittens sad (Score:5, Informative)
here [swin.edu.au] 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 (Score:5, Informative)
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 (Score:5, Informative)
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 (Score:5, Informative)
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. .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.
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.
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.
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posting anonymous because i burned all my mod points in this thread. out of interest, would you care to provide any examples for (3) and (4)? i'd imagine that with (3) you're thinking things like chaplygin gases, but how about (4)?
you're also missing at least the following
1.5) The hypotheses between 1997 and 2005, which are very similar to the current hypotheses. Given that SN1a data came along in 1997 and the Lambda CDM model was pretty much immediately adopted as standard, with various "dark energies" soo
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At one point, I read an article that refuted dark matter. (i'm certain i found it here on Slashdot) Dark matter was necessary to marshall the galaxy into its spiral shape. But these researchers realized that as the galaxies rotated, the stars at the outside edges of the galaxy were moving at a significant fraction (like 1 or 2 percent) of the speed of light. Relativity then causes the apparent mass of these stars to increase. Due to the squared term, 1% only leads to a 0.01% increase in appearent mass,
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Still reading. :-)
Thanks for the info. Pity the theory didn't stand up; I liked the "oh hey, the missing matter has been shining away brightly, running and waving 'Look at me! Look at me' the whole time."
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Not quite. Nobody's claiming that dark energy has any sort of intelligence or self awareness.
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May Cthulhu strike you down for this heresy.
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Our observations of the universe show that there is something affecting its structure on a massive scale. So we use dark energy and dark matter as placeholders until we can figure out what it is.
Now, if we were able to scientifically observe and quantify magic, resurrections, and the power of prayer? Then yes, it would be similar to saying "god" exists. But until you do that, the two are nothing alike.
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So hopefully others can find it
From my submission last week (the 19th), http://slashdot.org/journal/265330/Dark-energy---real [slashdot.org]
http://arxiv.org/abs/1104.2948 [arxiv.org]
""We present precise measurements of the growth rate of cosmic structure for the redshift range 0.1 z 0.9, using redshift-space distortions in the galaxy power spectrum of the WiggleZ Dark Energy Survey. Our results, which have a precision of around 10% in four independent redshift bins, are well-fit by a flat LCDM cosmological model with matter density p
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What they did is in fact rather easy to explain. First, the background. The early universe, right after its birth, was so small that sound waves could propagate thru it in so-called baryon acoustic oscillations. Concentrations of matter caused gravitational collapses that rebounded in radiation-forced implosions, creating bubbles - roughly spherical voids surrounded by matter. Since everything happened at once, the bubbles were of the approximately same size (think opening a soda can - you don't get inch-di
WTF Grammar (Score:5, Funny)
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Or:
Einstein is correct, as, so far, usual.
Very ugly either way...
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Looks like a case of attack of the touchpad to me....
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Or ...
"Einstein is correct, as usual (so far)."
Or ...
"Enstein is correct, as - so far - usual."
Or ...
"As usual, Einstein is correct. So far."
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Except Einstein isn't usually correct. E.g., he didn't believe Heisenberg's uncertainty principle, and his first four proofs of E=mc^2 were flawed. It's just that his successes outshine his mistakes, so the latter are forgotten, as so far, usual.
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Or ...
"Is Einstein correct so far? As usual."
Or ...
"So, Einstein is far? Correct, as usual."
Or ...
"As Einstein, far is correct. So usual.
Or ...
"Einstein! Far is usual! Correct, ass."
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I think they call this grammar nazi baiting.
Re:WTF Grammar (Score:5, Funny)
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Segfault on untrusted data input? Sounds like a security vulnerability to me. Better patch that - you wouldn't want somebody to exploit your brain and take control. What privilege level do you run your grammar parser at? Also, what instruction set does it use? Is there already a shellcode available for it?
Text-reading exploits (Score:2)
Segfault on untrusted data input? Sounds like a security vulnerability to me. Better patch that - you wouldn't want somebody to exploit your brain and take control.
Yup, there are a few exploits reported in the wide, that use specially crafted texts to inject malicious payloads, and turn non-patched brains into raving maniacs :
The Bible, the Quran, various books about Dianetics, the biography of Michael Jackson....
Einstein was right? (Score:1)
(Not disagreeing with the result, but the einstein-fanboying in TFA is a little irritating)
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fanboying einstein is better than fanservicing einstein
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Haha.
I know someone who wrote a fan service about Albert Einstein and Isaac Newton...
She is an odd one.
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TFA has that quote in it, so I guess you're doing einsteinfanboying if they are.
That is the core of the joke being made after all.
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Re:Einstein was right? (Score:5, Insightful)
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.
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I'm a bit murky. I last read an Einstein biography about 8 months ago...
Was it that Einstein believes the universe wasn't expanding or that he capitulated to the common held belief that the universe wasn't expanding? In one case you had Einstein believing wrong and the other had Einstein kowtowing to the status quo.
Re:Einstein was right? (Score:4, Insightful)
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It's not *that* much of a leap of physical intuition. On the one hand if you look at relativity as a collection of partial differential equations it crops up inevitably as an integration constant that would otherwise be *assumed* to be zero. So in principle it's there at the outset and is just arbitrarily removed.
On the other hand if you view relativity in any other way the "cosmological constant" emerges one way or another -- as the constant term in a Laurent expansion of a more accurate Lagrangian density
Move along (Score:1)
Einstein was wrong most of the time (Score:1)
Even if the percentage when he was right was a lot higher than most everyone on this planet. He made plenty of mistakes. Furthermore, stop thinking of him as an old man with the funny hair. He was still young when he did his important work, while most of the mistakes came later.
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Correct, at one time he was a young man with funny hair.
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Correct, at one time he was a young man with funny hair.
Are Y'oo Serious?
A bit of a stretch... (Score:4, Insightful)
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Don't you mean, 11 [youtube.com]?
Fixed that for you.
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what if dark matter goes all the way up to eleven?
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That may be the reason it goes off the charts. Calibrating it for dark matter will make it quite wrong for detecting dark energy.
(a) current theory (Score:3)
and current theory uses dark energy to explain
The most popular current theory does - there are competitors as well. But, yeah, this is useful because those working on all the theories can keep on going, knowing that they're more likely to be on the right track than they were yesterday.
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Re:A bit of a stretch... (Score:5, Insightful)
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.
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If you instead propose that the universe oscillates in size, then it would become obvious that expansion will first be accelerating then decelerating, sinusoidally. Dr.Randall Mills proposes that the acceleration is caused by the stars "burning" matter into energy, uncurving space. Eventually matter will all turn to energy or black holes, black holes will over time capture all the energy and by becoming more massive will cause space contraction. Then something magical will happen and the black holes will ex
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The Verse is expanding, we don't know why, so we call it "dark energy", would it be better to call it "boom"?
Lots of theories, few proofs.
The Wiggles?? (Score:1)
You spelt Wiggles wrong, btw.
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I guess the Wiggles [wikipedia.org] are really taking their child education program seriously. You spelt Wiggles wrong, btw.
I wish I could find the reference, but I remember a few years ago of an astronomer(?) calling some celstial objects B1 and B2 after Bananas in Pyjamas. So the Wiggles are justplaying catchup.
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Seriously, though; The music industry can keep Blue.
But does it proof the dark energy existence ? (Score:2)
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It does prove (again) that there is something that causes accelerating expansion, they call it dark energy because they don't know what it is.
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Yes. This is correct. The Einstein field equations without a cosmological constant fail to describe the universe. Thus those equations are incorrect or incomplete. However, when we add a cosmological constant, the resulting equations do correctly describe the universe. We don't know, on a microscopic level, what sort of effect produces the term in the equations called the cosmological constant, but we do know some very general features of what sort of microscopic phenomena could produce that term. Mor
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So you know, for example, that there is nothing that has mass and doesn't interact with photons? How do you do that, divine revelation?
And, yes, the current theories don't work with observable matter and energy, much as pre-quantum physics couldn't account for things like black-body radiation. When that happens, physicists come up with wacky "what-if" ideas, such as the idea that light (known to be a wave) could only come in packets of a certain "size". Other physicists start playing with those ideas,
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Ok It seems they proof the universe was expanding at an accelerating rate. But does/why it proof the dark energy existence ?
Because dark energy is defined as a substance (quantity, thing, whatever) that causes accelerated expansion of the universe.
It sounds goofy but this is legitimate in science, especially physics. For instance, what is a wave function? Well, it's the variation over time and space of "some quantity". What quantity? What IS it? We don't know, however, we can do math on it and arrive at s
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Dark energy refers to a specific general relativistic situation. While we don't know why that situation occurs, we have done measurements (including this one) confirming that the particular inputs we put into the equations of GR reproduce the characteristics of the universe to within theoretical and experimental uncertainty.
There are lots of ways that one could construct an alternative theory that would also describe a universe expanding at an accelerating rate that would not agree with our observations.
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Educational Songs (Score:2)
Re:Educational Songs (Score:5, Funny)
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!
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(+15, all my mod points, Funny)
Really Slashdot (Score:3)
WTF has Einstein to do with this?!
Of course studies of dark energy are deeply conneted to general relativity. But don't throw names like you pretend you know what you are doing.
This is becoming ridiculous, this is like "Well, I drove 100Mi at 50MPH and it took 2 hours, looks like Newton is right again"
Cosmological Constant (Score:5, Informative)
WTF has Einstein to do with this?!
I assume TFS was referring to the cosmological constant [wired.com] - some have figured that Dark Energy is the mechanism behind the lambda* in Einstein's equations.
*someday Unicode will work on Slashdot...
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Einstein added the cosmological constant because he felt at the time that the universe should be steady state, it shouldn't have an identifiable end. The cosmological constant was meant to exactly cancel out the force of gravity at cosmological scales so that the universe could effectively last forever. We know now that this is most likely not the case, eventually the expansion will accelerate so rapidly that individual subatomic particles will be torn to pieces by it. So really, Einstein was right in th
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As far as I know, Einstein added the cosmological constant because the equations he was solving hod true for any value of it. Then he choosed some value different from zero because he wanted to make the universe static.
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Couple of problems with that:
* Gravitationally-induced time dilation is a local effect--the degree of dilation for an observer depends on the strength of the local gravitational field at that observer's location. And while the universe's expansion does contribute some ongoing changes to the local gravity field strengths at every point throughout the universe, the size of those changes is miniscule compared to the absolute strength of even the earth's gravity at the planet's surface. The observed eff
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IHPBT? Isn't that the code in Doom 1/2 for infinite ammo? *grin*
More Accurate Description (Score:5, Informative)
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Dark energy and dark matter have not yet been observed or measured in any way.
Measuring the expansion of the universe is measuring dark energy. Perhaps you meant that they haven't been directly measured (that is what the "dark" implies, after all), although there are problems with that adjective: most things in physics these day are only ever indirectly measured.
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Oh my yes, there's a huge range of how directly something is measured. Dark matter and energy are highly indirect, although with this result, there's more strength behind dark energy.
But then, physicists don't going around thinking that they've proven that there's this "stuff" out there called "dark matter". Only Slashdotters think that. They're not "things", they're words to refer to the gap between two observations. Those gaps happen to both be mass-like if we make the world fit a model that seems quite r
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If it's a force, why is it called energy? Shouldn't it be Dark Force, or Dark side of the Force?
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1 - Dark energy is the name of whatever causes the universe to expand.
2 - A team of researches confirm that the universe is expanding.
1 & 2 -> A team of researches confirm that dark energy (whatever it is) exist.
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In science related journalism, when you read "X confirms Y", the proper interpretation is usually "X confirms a prediction implied by Y".
Presumption of static images (Score:2)
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It's a multifaceted calibration.
There are stars with predictable brightnesses that are close enough to exhibit parallax.
Those same stars in other galaxies then give us a distance to other galaxies.
There are other events, supernovas etc that are known to have an upper limit in brightness. From that we can estimate distances to far away galaxies.
Or we can use redshift to estimate the same distances.
Of course there are wide error bars. But it's not just a random guess.
And what is this "mathematical models with
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Which is great but have we ever correlated redshift to distance or speed with actual observations or just mathematical models? I'm all for mathematical models but when they don't have actual observational support I wonder a tad...
There are a number of techniques for determining distance based on relative luminosity (stars classed Cepheid variables were originally used by Hubble to determine the distance of objects). The technique originally used to determine that the expansion of the universe was actually accelerating used Type Ia supernova, which pretty much all have exactly the same luminosity. Since the luminosity of those objects is a known quantity, the distance is easily determined. So, yes, there is plenty of observational
Nothing to see here (Score:3)
Slashdot posts these articles about dark energy every 6 months, but nothing ever makes it to consumers. Let me know when Dark Energy generators are available at my local Home Depot, then I'll be interested.
Now you see... (Score:2)
...the *power* of the dark side.
Whatcha' doin'? (Score:2)
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Semi off-topic, but... (Score:2)
Since this post will attract cosmologically inclined folks:
The popular press keeps saying that some emissive DSO is, for instance, 11m light years away, and that means that its light took 11m years to get to us.
Various cosmological theories, however, tell us that the universe is, and has been, expanding, even faster than light at some points, by virtue of the space expanding.
But... If space was smaller previous to now (which proposition seems like it would always be true if space is constantly expanding), t
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