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Dark Energy Confirmed By Australian WiggleZ Sky Scan

Posted by Roblimo on from the peering-deep-into-the-cosmos dept.

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* .

85 of 131 comments (clear)

  1. Bad pop-sci writing makes kittens sad by Sneftel · · Score: 5, Informative

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

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    1. Re:Bad pop-sci writing makes kittens sad by Dachannien · · 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.

    2. Re:Bad pop-sci writing makes kittens sad by Nadaka · · 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.

    3. Re:Bad pop-sci writing makes kittens sad by Joce640k · · Score: 1

      Not quite. Nobody's claiming that dark energy has any sort of intelligence or self awareness.

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    4. Re:Bad pop-sci writing makes kittens sad by Nadaka · · Score: 2

      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.

    5. Re:Bad pop-sci writing makes kittens sad by Archangel+Michael · · Score: 1

      May Cthulhu strike you down for this heresy.

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    6. Re:Bad pop-sci writing makes kittens sad by Artifakt · · 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.
      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.

      --
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    7. Re:Bad pop-sci writing makes kittens sad by Anonymous Coward · · Score: 1

      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" soon postulated, you're missing a big chunk of time there. And given that WMAP1 came out in 2003, you're also missing the dramatic confirmation that WMAP1 brought with it.

      5) Inhomogeneities, which can mimic some of the effects of dark energy. All the models that have been looked at so far are pure toy models and no-one is pretending that they're a valid model of the universe, but they're a proof of concept that local structure can have a significant effect -- and it would take an idiot to pretend that there isn't local structure near us.

      6) An inaccurate model. It would also take an idiot to pretend that LCDM (or variations) isn't a superb model. It fits almost every prediction made thus far and frankly we have no serious competitor. But LCDM itself is "filled with ad-hoc assumptions", the most important of which is that we're pretending we know how to construct an average in GR. We don't and every attempt (probably including Zalaletdinov's) is gauge- or frame-variant. And yet we blithely say "the universe on average obeys a Robertson-Walker metric, so we plug it into the Einstein equations and...". Except that the average dynamics are not the dynamics of the average -- even if we can't perform the average we *can* say that! Likewise, the average geodesics are not the geodesics of the average. So we're definitely workign with the wrong model. Of course, any studies of this so far have been incomplete and tend to find corrections that act as curvature or dark matter and are frankly impossible to interpret, but even so...

    8. Re:Bad pop-sci writing makes kittens sad by tqft · · Score: 1

      So hopefully others can find it
      From my submission last week (the 19th), http://slashdot.org/journal/265330/Dark-energy---real

      http://arxiv.org/abs/1104.2948
      ""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 parameter Omega_m = 0.27."
      Comments: 17 pages, 11 figures, accepted for publication by MNRAS"

      --
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      Quant
    9. Re:Bad pop-sci writing makes kittens sad by vuo · · Score: 1

      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-diameter bubbles, do you?). After the universe had expanded, the surfaces of the bubbles formed the cosmic filamentary structures we see today; galaxies formed at the densest intersections of these bubbles and filaments.

      Second, the work. It's hard to figure out what's the distance or speed of a galaxy by just looking at it. Redshift is the most obvious, giving you speed and consequently distance, and that was used here first. Supernovas are one solution, functioning as standard candles. Their trick was to use the filamentary structure of the universe itself as the measuring stick. Equally sized bubbles meant that while most galaxy-galaxy distances are random, you still get an overdensity of 150 megaparsec separations. These are between two galaxies on opposite sides of the same bubble. Exploitation of this fact allowed the extend the redshift survey more reliably to larger distances. This gave them the world's farthest-reaching "radar gun". The result was that smooth accelerating expansion was confirmed for half of the age of the universe.

    10. Re:Bad pop-sci writing makes kittens sad by AJNeufeld · · Score: 1

      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, but they ran the numbers for the distributions of stars, their orbital distances and velocities, and found that including this relativistic effect completely eliminated the need for dark matter in the formation of the shape of the galaxies.

      It has been years, and dark matter is still being searched for. Was this research refuted? Does anyone remember it?

    11. Re:Bad pop-sci writing makes kittens sad by AJNeufeld · · Score: 1

      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."

  2. WTF Grammar by degeneratemonkey · · Score: 5, Funny

    Last part of summary segfaults my internal parser.

    1. Re:WTF Grammar by Kokuyo · · Score: 1

      Or:

      Einstein is correct, as, so far, usual.

      Very ugly either way...

    2. Re:WTF Grammar by robthebloke · · Score: 1

      "So far, Einstein is correct, as usual."

      Looks like a case of attack of the touchpad to me....

    3. Re:WTF Grammar by TheLink · · Score: 5, Funny

      That confirms the existence of dark grammar.

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    4. Re:WTF Grammar by multisync · · Score: 2

      Or ...

      "Einstein is correct, as usual (so far)."

      Or ...

      "Enstein is correct, as - so far - usual."

      Or ...

      "As usual, Einstein is correct. So far."

      --
      I don't care why you're posting AC
    5. Re:WTF Grammar by StikyPad · · Score: 1

      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.

      --
      https://www.eff.org/https-everywhere
    6. Re:WTF Grammar by Anonymous Coward · · Score: 1

      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."

    7. Re:WTF Grammar by Austerity+Empowers · · Score: 1

      I think they call this grammar nazi baiting.

    8. Re:WTF Grammar by cbhacking · · Score: 1

      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?

      --
      There's no place I could be, since I've found Serenity...
  3. Einstein was right? by m50d · · Score: 1
    Would that be when he called the cosmological constant "the biggest mistake of my life"?

    (Not disagreeing with the result, but the einstein-fanboying in TFA is a little irritating)

    --
    I am trolling
    1. Re:Einstein was right? by austinpoet · · Score: 1

      fanboying einstein is better than fanservicing einstein

    2. Re:Einstein was right? by nedlohs · · Score: 1

      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.

    3. Re:Einstein was right? by Nadaka · · Score: 1

      Haha.

      I know someone who wrote a fan service about Albert Einstein and Isaac Newton...

      She is an odd one.

    4. Re:Einstein was right? by chemicaldave · · Score: 1

      Doesn't make any less correct. I'm reading into it as "Oh, hey, whaddaya know. Looks like he was right." Which he has consistently been good at.

    5. Re:Einstein was right? by bunratty · · Score: 4, 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.

      --
      What a fool believes, he sees, no wise man has the power to reason away.
    6. Re:Einstein was right? by Talderas · · Score: 1

      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.

      --
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    7. Re:Einstein was right? by pclminion · · Score: 3, Insightful

      Einstein saw it as a huge mistake, but it wasn't. Current evidence suggests that the value of the cosmological constant is not zero, it's some small positive number. If Einstein had not put the cosmological constant in in the first place, we wouldn't have been able to assign a value to it. His blunder was the assumption of a static universe, not a cosmological constant. The cosmological constant was a leap of physical intuition -- it has a value other than Einstein thought it should have, but so what? He was obviously a bit smarter than most of us :-)

    8. Re:Einstein was right? by Anonymous Coward · · Score: 1

      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, or as a low-energy term coming out of some higher-energy modified gravity theory, or the basic identification which is as the energy of the vacuum itself. Getting the right *numbers* is tough, but that's a different matter; a constant term is fairly inevitable. And Einstein only got the "right" number by putting it in by hand, and his value was well out from the current observations and only of an equivalent order of magnitude because he wanted it to balance the universe while we want it to slightly accelerate it.

  4. Move along by dimethylxanthine · · Score: 1

    This is not the energy you are looking for...

  5. Einstein was wrong most of the time by Anonymous Coward · · 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.

    1. Re:Einstein was wrong most of the time by Nadaka · · Score: 1

      Correct, at one time he was a young man with funny hair.

    2. Re:Einstein was wrong most of the time by UncleTogie · · Score: 1

      Correct, at one time he was a young man with funny hair.

      Are Y'oo Serious?

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  6. A bit of a stretch... by Eggplant+Jeff · · Score: 4, Insightful

    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!"

    1. Re:A bit of a stretch... by Henriok · · Score: 1

      If they had built such a detector, wouldn't they the charts be calibrated to about the expected amount of dark matter?

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    2. Re:A bit of a stretch... by mangu · · Score: 4, 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.

    3. Re:A bit of a stretch... by Dyinobal · · Score: 1

      Everyone knows the standard detector only goes up to nine thousand. The Dark Mater was clearly over nine thousand if it was off the charts.

    4. Re:A bit of a stretch... by Dynetrekk · · Score: 1

      Don't you mean, 11?

    5. Re:A bit of a stretch... by berashith · · Score: 1

      what if dark matter goes all the way up to eleven?

    6. Re:A bit of a stretch... by khallow · · Score: 1

      This is correct. They aren't claiming there is some sort of unseen energy. That's just the name that stuck. If they're seeing an expanding universe, they're seeing "dark energy".

    7. Re:A bit of a stretch... by amRadioHed · · Score: 1

      Don't you mean, 11?

      Fixed that for you.

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    8. Re:A bit of a stretch... by marcosdumay · · Score: 1

      That may be the reason it goes off the charts. Calibrating it for dark matter will make it quite wrong for detecting dark energy.

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      Rethinking email
    9. Re:A bit of a stretch... by Paracelcus · · Score: 1

      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.

      --
      I killed da wabbit -Elmer Fudd
  7. The Wiggles?? by Gumbercules!! · · Score: 1

    I guess the Wiggles are really taking their child education program seriously.

    You spelt Wiggles wrong, btw.

    1. Re:The Wiggles?? by OzPeter · · Score: 1

      I guess the Wiggles 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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    2. Re:The Wiggles?? by L4t3r4lu5 · · Score: 1

      Further evidence of a music career preceding physics

      Seriously, though; The music industry can keep Blue.

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  8. But does it proof the dark energy existence ? by nithril · · Score: 2

    Ok It seems they proof the universe was expanding at an accelerating rate. But does/why it proof the dark energy existence ?

    1. Re:But does it proof the dark energy existence ? by Anonymous Coward · · Score: 1

      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.

    2. Re:But does it proof the dark energy existence ? by nithril · · Score: 1

      Something or maybe equation is .. wrong ? There is no dark matter nor dark energy, just incomplete/incorrect equation.

    3. Re:But does it proof the dark energy existence ? by pclminion · · Score: 1

      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 specific predictions which are confirmed by experiment. Nobody to this day knows what "it is" with respect to the wave function, yet we all accept that it's a legitimate thing, mathematically at least.

    4. Re:But does it proof the dark energy existence ? by The_Wilschon · · Score: 1

      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. The fact that our observations (and in particular the new observations of the WiggleZ experiment) agree with the particular theory called "Dark Energy" (or more accurately the Lambda-CDM model) and disagree with lots of other potential theories is the subject of the article.

      --
      SIGSEGV caught, terminating

      wait... not that kind of sig.
    5. Re:But does it proof the dark energy existence ? by The_Wilschon · · Score: 1

      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. More specifically, an amount of energy which is proportional to the volume of space would produce a cosmological constant term. Since we know with a reasonable degree of certainty that a) the phenomenon in question is an energy type phenomenon, and b) it does not appear to couple to the photon, it is a form of energy which is "dark", and we call it "dark energy".

      I really wish that this "dark matter and dark energy just mean scientists have no idea what they are talking about" meme would die. It simply isn't true. There are some very specific things that we don't know about dark matter and dark energy. There are a lot more things that we do know about them.

      --
      SIGSEGV caught, terminating

      wait... not that kind of sig.
    6. Re:But does it proof the dark energy existence ? by david_thornley · · Score: 1

      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, and finding other things the ideas could explain, predictions of what we could observe under the ideas, and ways in which we could test those ideas to see which have promise and which don't.

      It turned out that black-body radiation wasn't explained by classical physics, but required some of the basics of quantum mechanics. It turned out that the differences between Mercury's predicted and observed orbit weren't due to another planet inside Mercury's orbit (named "Vulcan"), but were evidence of some really strange ideas called General Relativity. To a physicist of the 19th Century, quantum mechanics and general relativity would have seemed far wackier than, say, matter and energy that can't be observed using modern observation techniques.

      --
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  9. Educational Songs by VorpalRodent · · Score: 1

    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...

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    1. Re:Educational Songs by drinkypoo · · 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!

      --
      "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
    2. Re:Educational Songs by Vegeta99 · · Score: 1

      (+15, all my mod points, Funny)

  10. Really Slashdot by JamesP · · Score: 2

    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"

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  11. Re:Einstein is always right by robthebloke · · Score: 1

    Awesome! I can't wait to see the history of the 21st century according to Charlie Sheen!

  12. (a) current theory by bill_mcgonigle · · Score: 2

    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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  13. Cosmological Constant by bill_mcgonigle · · Score: 5, Informative

    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...

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    1. Re:Cosmological Constant by MozeeToby · · Score: 1

      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 that there is a cosmological constant (and do note that he changed his mind later and removed it from the equations), but he was very much so wrong about what the value of the constant would be and the effects that it would have on the universe.

    2. Re:Cosmological Constant by marcosdumay · · Score: 1

      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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  14. More Accurate Description by Lluc · · Score: 5, Informative

    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.

    1. Re:More Accurate Description by blueg3 · · Score: 1

      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.

    2. Re:More Accurate Description by Anonymous Coward · · Score: 1

      If it's a force, why is it called energy? Shouldn't it be Dark Force, or Dark side of the Force?

    3. Re:More Accurate Description by marcosdumay · · Score: 1

      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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      Rethinking email
    4. Re:More Accurate Description by Lluc · · Score: 1

      You are correct: right after I hit "post" I wanted to add the word "directly". It is a bit of a tricky word to use, though. I think many quantities in physics are measured in much more reasonable ways than dark matter and energy. As far as I'm concerned, dark matter and dark energy are explained by "our current theories don't make sense without them, so they gotta be there even though we have no evidence."

    5. Re:More Accurate Description by blueg3 · · Score: 1

      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 reasonable and has otherwise held up, so the gaps get the admittedly-confusing names "dark matter" and "dark energy".

  15. Presumption of static images by Drethon · · Score: 1

    So we've basically taken a snapshot of the universe (since the time span we've been observing is a minute fraction just compared to a planet, much less the universe) and made definite measurements of movement from this still picture. I don't know, something always sounded wrong about this...

    1. Re:Presumption of static images by ThatMegathronDude · · Score: 1

      Measurements of galactic movement are based on the fact that all other galaxies have a redshift, i.e. they are moving away from us and the doppler effect has shifted their light frequency toward the red end of the spectrum.

    2. Re:Presumption of static images by Drethon · · Score: 1

      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...

    3. Re:Presumption of static images by locofungus · · Score: 1

      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 without observational support". The whole point of a mathematical model is that it explains observations. There are two types of model - empirical, where the model agrees with the observations but we don't understand why the model should agree (the early atomic emission spectroscopy results fell into this category) and physical, where the model is based around our understanding of the underlying physics, those same atomic spectroscopy models are now physical models given that we now understand emission spectra based on the ideas of atomic number, electron shells etc

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    4. Re:Presumption of static images by Curunir_wolf · · Score: 1

      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 evidence, both of the expansion, and that the expansion is getting faster, not slowing.

      --
      "Somebody has to do something. It's just incredibly pathetic it has to be us."
      --- Jerry Garcia
  16. Nothing to see here by Jeremi · · Score: 2

    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.

    --


    I don't care if it's 90,000 hectares. That lake was not my doing.
  17. Re:Time dilation by MoralHazard · · Score: 2

    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 effects of lambda (cosmological constant, dark energy, whatever) are a whole lot bigger.
      * Time dilation works opposite to your description, i.e., the GREATER the local mass density (and therefore the more intense the local gravitational field) the faster time will move relative to the rest of the universe.
      * Einstein's GR includes the relativity of time and space in the model, as specific terms OTHER than lambda. Lambda is the part of the model that *cannot* be explained by anything else we already know about.

    I know, I know: IHPBT. I needed something to do while my coffee was cooling.

  18. Re:Time dilation by BertieBaggio · · Score: 1

    IHPBT? Isn't that the code in Doom 1/2 for infinite ammo? *grin*

    --
    If all you have is a grenade, pretty soon every problem looks like a foxhole -- MightyYar
  19. Now you see... by Chris+Mattern · · Score: 1

    ...the *power* of the dark side.

  20. Re:Dark Energy/Matter Podcast by Cornell Universit by thermalgreen · · Score: 1

    Cool!

  21. Semi off-topic, but... by fyngyrz · · Score: 1

    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), then arriving light that appears to be from a source that is now 11m light years away didn't have to cross 11m light years, because, for instance, 5.5m years ago, it had traveled more than half way here, because at that time, the distance was less than 11m light years.

    And consequently, said DSO's light hasn't been under way for 11m light years, but instead, less.

    No? Yes? Help me out here, I'm drowning. Relatively speaking.

    --
    I've fallen off your lawn, and I can't get up.
    1. Re:Semi off-topic, but... by Muros · · Score: 2

      Nope. You're on the right track, but looking at it the wrong way. We can make rough estimates of how far away something is based on how far away it appears to be, what relative velocity/acceleration it appears to have, etc. So something that appears to be 11Mly away could be 20Mly distant.

  22. Re:Scientific Method by Dan+Ost · · Score: 1

    In science related journalism, when you read "X confirms Y", the proper interpretation is usually "X confirms a prediction implied by Y".

    --

    *sigh* back to work...
  23. Re:Dark Magnetism by parineum · · Score: 1

    Dark magnetism, how does it work?

  24. Whatcha' doin'? by Geminii · · Score: 1

    Hey, Starscream, I know what we're going to do today!

  25. Text-reading exploits by DrYak · · Score: 1

    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....

    --
    "Sufficiently advanced satire is indistinguishable from reality." - [Tips: 1DrYakQDKCQ6y52z6QbnkxHXAocMZJE61o ]