Follow Slashdot blog updates by subscribing to our blog RSS feed

 


Forgot your password?
Close
typodupeerror
×
Space Science

Dark Energy Confirmed 102

Posted by michael from the universe-is-like-duct-tape dept.
bill_mcgonigle writes "By correlating the results of the Sloan Digital Sky Survey and the Wilkinson Microwave Anisotropy Probe, astronomers have confirmed the existence of dark energy. While gravity attracts, dark energy repels, so by comparing the positions of millions of galaxies and their red-shifts with the temperature map of the early universe, evidence was found for dark energy on the scale of 100 million light years. "Dark energy, whatever it is, is something that is not attracted by gravity" said David Spergel, a Princeton University cosmologist and a member of the WMAP science team. "We are finding that most of the stuff in our universe is abnormal in that it is gravitationally repulsive rather than gravitationally attractive," said Albert Stebbins of the Fermi National Accelerator Laboratory. The universe is expanding at an accelerating rate, a switch that happened about 6.3 billion years ago, before which the expansion was decelerating."
This discussion has been archived. No new comments can be posted.

Dark Energy Confirmed More

Dark Energy Confirmed

Comments Filter:

  • Occam's razor (Score:2, Interesting)

    by ka9dgx ( 72702 ) *
    Rather than assuming some bizarre physics of gravitons where they pull something they ram into, why not take a simpler approach and assume that they push things along, just like a baseball and the milk bottle at the faire?

    The earth stops some of them passing through, and thus the ones from above us push us down. All the standard laws of physics still work on the local level, and nobody has to get a migrane trying to wrap their heads around weird concepts.

    This is much simpler than "dark energy"... the fart

    • Please perform the following thought experiment. If you insist on perceiving interactions as "particles ramming into each other" consider the electromagnetic interaction. In the case of two electrons (a and b), a emits a photon, which "rams" into b and b moves "away" from a. OK, now make b a positron, a emits a photon, which "rams" into b and b moves "towards" a. Perhaps the idea of particles "ramming" into each other needs to be reconsidered.

    • Re:Occam's razor (Score:2, Interesting)

      by GeoGreg ( 631708 )
      The whole trick here will be to fit all the observations together into a consistent model. People have been trying for a long time now to reconcile general relativity (i.e., the concept that gravity is equivalent to warped space-time) with quantum mechanics. Nobody has yet done it, and dark energy and dark matter seem to be bringing up more problems. My semi-educated guess is that significant new physics will be required to reconcile everything. It might be revolutionary on the same scale as Einstein, B
    • I'm not sure how old that suggestion is. Several centuries old I think. It falls apart the moment you try to do any kind of numerical computation with it. Try it and see.

    • Re:Occam's razor (Score:5, Informative)

      by iggymanz ( 596061 ) on Thursday August 07, 2003 @01:32PM (#6637306)
      Over 200 years ago massive objects were observed to attract each other and deflect a torsion balance in a direction at a right angle to the earth's gravitational field. So your interesting hypothesis (and I do like it) needs some modification.
      • Why the hell was this comment marked informative?

        What, the earth can be a source of gravity (or the blocking of an external pressure), and a heavy mass can't be?

        If the earth blocks .0000001% (or another sillily small percentage) of the "gravitons" passing through it, you would have a net force pushing you down to the earth. If a heavy lead ball blocked 0.00000000000001% of the gravitons passing through it, you would get a net push to the side (or whatever direction the ball is from the test mass)

        It work
        • aaahh, but then the "blocking" is observed to be EXACTLY proportional to the mass (as observed for past 200 years), *not* the density of the object.....THAT is the problem.

    • I would rather start playing with the concept of negative mass, since gravity is still a by-product of, to me.

    • Force-carrying particles. (Score:5, Informative)

      by Christopher Thomas ( 11717 ) on Thursday August 07, 2003 @03:06PM (#6638595)
      Rather than assuming some bizarre physics of gravitons where they pull something they ram into, why not take a simpler approach and assume that they push things along, just like a baseball and the milk bottle at the faire?

      You appear to be using an overly-simplistic model of what force-carrying particles are.

      The classical model of force involves "fields" - continuous distributions of force about their sources (e.g. an electric field that varies as the inverse square of distance from an object with charge, or a gravitational field that varies as the inverse square of distance from an object with mass).

      When quantum mechanics came along, it was realized that these fields weren't continuous in all senses - disturbances in the field could only come in discrete packets. These are the force-carrying particles.

      A graviton doesn't "ram into" anything. It's a moving ripple in the gravitational field of an object. The net effect of all gravitons (real and virtual) about an object with mass is to produce an attractive force on other massive objects nearby.

      Similarly, a photon is a moving ripple in the electromagnetic field, with the net effect of all of the virtual photons in the vicinity of a charged object being to attract or repel other charged objects in the area.

      The properties of gravitons are less certain, because it's hard to build a quantized version of Einsteinian gravity, but this is the general idea behind force-carrying particles (in force-carrying contexts, they can be thought of as the minimum (quantized) disturbance of a classical-looking field of force).
    • I have no idea why your comments are modded up. Your suggestion lacks any scientific merit and is wrong on sooo many levels. I'm not really sure it merits a response, but I'll try.

      Your suggestion amounts to either "there is no such thing as pull forces, objects can only push" or "the only forces that exist are those transferred by physical contact, ie things bumping into one another".

      Lets assume (incorrectly) that your suggestion is true. What are some of the consequenses of this assumption? First,

    • Refuted by Feynman (Score:1, Interesting)

      by Anonymous Coward

      Feynman discusses, and refutes, a similar theory of gravity in The Character of Physical Law [barnesandnoble.com] .

      If I recall correctly it is in the chapter where he establishes why physical law must be expressed in terms of equations. Common sense ideas like the one you mentioned are tempting, but don't seem to fit the facts we know.

    • Occam's Razor is a terrible way to logically reason something out. First of all, in science, one assumes an infinate number of factors which must be controlled for - secondly:

      Occam says: "God did it."

      Provide me with a simpler explanation that uses less entities?
      • Provide me with a simpler explanation that uses less entities?
        Positing the existance of an omnipotent, omniscient and thus (probably) infinitely complex being is NOT the simplest solution!


        Occam's razor works fine as a guiding principle.

        • That's exactly the point. Simplicity is an inherently subjective concept. God is not a good explanation for physical phenomena because there is no known way to test the hypothesis, not because the God explanation is any more or less "simple" than some other explanation. Occam's razor should not play a serious role in science until someone is able to provide an objective method for measuring the simplicity of an idea. I don't think it can be done.

    • Re:Occam's razor (Score:3, Interesting)

      by ka9dgx ( 72702 ) *
      Ok, I'm mystified by the /. rating system sometimes myself.

      I understand electromagnetic polarity, opposites attracting, etc... I don't want to play with the physics of that right now... just those darned unipolar gravitons.

      If you assume a very high flux of gravitons, all with a very low mass (or energy), and a low probability of interacting with a given unit of mass, the following conditions start to fall out of the math:

      • a sufficiently dense mass will stop a very small, but consistent fraction of the
      • Your idea is very, very silly and I strongly suggest you don't waste time with simulations. Imagine the planets are in alignment, as happens sometimes. They would then shield each other from this "global graviton flux" and the orbits would be perturbed. For that matter, you CANNOT have orbiting bodies in your system - that requires a centripetal force which you cannot provide.

  • Must be that gosh-darn Global Warming... (Score:1, Funny)

    by Anonymous Coward

    The universe is expanding at an accelerating rate, a switch that happened about 6.3 billion years ago, before which the expansion was decelerating.

    Must be that gosh-darn Global Warming...

    Paging Mr. Gore, Mr. Albert S. Gore...

  • Normal vs Abnormal (Score:4, Funny)

    by Inexile2002 ( 540368 ) on Thursday August 07, 2003 @12:16PM (#6636350) Homepage Journal
    "We are finding that most of the stuff in our universe is abnormal in that it is gravitationally repulsive rather than gravitationally attractive..."
    How can most of the universe be abnormal. Wouldn't the majority of the universe be "normal"? If most of the universe is repulsive instead of attractive (why did I think of the last three blind dates I've been on when I wrote that) then wouldn't repulsive be "normal". Right?

    Damn, now I'm thinking of Karen... talk about repulsive being normal.

  • What exactly was confirmed? (Score:1, Funny)

    by Anonymous Coward
    As far as I can tell, all that was confirmed was an unexplainable acceleration in the expansion of the universe.

    • As far as I can tell, all that was confirmed was an unexplainable acceleration in the expansion of the universe.
      An acceleration requires a force. A force needs energy to be created. The energy creating this force has eluded our detection, thus rendering it "dark." Ergo, Dark Energy. What's your point?
    • As far as I know and IANAA The temperature map of the universe is a glimpse into how the universe was behaving prior to the existance of matter. If the temperature map shows that there was epansion even before matter existed(and everything was energy) then we know that matter does not repel other matter. Energy repels matter and engergy hence Dark Energy and not Dark Matter makes up large amounts of the universe AFAIK

  • Clever names. (Score:2, Funny)

    by Spudley ( 171066 )
    ...said Albert Stebbins of the Fermi National Accelerator Laboratory.

    Why do all the really clever people in the world have to be named Albert? ;-)

    • Albert Gore, Super Genius (Score:1, Funny)

      by Anonymous Coward
      "Why do all the really clever people in the world have to be named Albert? ;-)"

      Except that that b00b who went around saying that he invented the Internet.


    • > Why do all the really clever people in the world have to be named Albert?

      The really smart ones are all named Milhouse, but they tend to pick up nicknames along the way.

  • When I first studied cosmology, I wanted the theories to work out so our universe would be a series of Big Bangs that would go on infinitely. This would mean we were all part of a never ending series of events that can lead to sentient life. Now that Dark Matter is gaining acceptence, it changes things.

    If the Big Bang was a one time event, and the Universe will expand forever then the question is how did this first and only Big Bang happen. What forces were at work prior to the Big Bang?

    While this
    • I think the "ultimate question", which is probably unanswerable, is "why does anything bother to exist?" It could be a one-time Big Bang, an infinite number of universes generated from "quantum foam", an endless cycle of bangs and busts, or a cosmic turtle. But, I don't know if the answer of "why is it here" can be answered from within the Universe. Maybe the best answer is "why not?".
    • Well here's one possibility [space.com]. If that's possible, anything is.
      • Well here's one possibility. If that's possible, anything is.

        See my previous messags on this topic in the "end of the universe" article (click on my user info).

        Summary: This makes improbable assumptions. When most physicists talk about "brane theory", they mean something else (a variant of string theory).

    • Now that Dark Matter is gaining acceptence, it changes things.

      Also, this particular article is about "dark energy", which is considered different from "dark matter". Not that it matters.

      Larry

    • Given it started (and supposedly) will finish on the other side of an event horizon - this is a hopeless quest.

      Q.

    • What forces were at work prior to the Big Bang?
      "Prior to the big bang" is almost exactly as meaningful as "North of the North pole". The 3+1 dimensional coordinate system (3 space, 1 time) that can be neatly spplied to events in most regions of the universe fails in the presence of too much energy, as in a black hole, or at the big bang.
  • Since we've only been able to play with very small amounts of antimatter we've never been able to see it's affects with regard to gravity. Maybe there's a whole lot more antimatter in the universe than we thought, and since it's the "opposite" of normal matter, maybe it has a different affect on space time, like producing anti-gravity. Of course my quack theory doesn't explain how everything doesn't come in contact and blow up, but I just barely have a HS diploma, and weird shit like this gives me a headach
    • Antimatter doesn't have negative mass. We've observed antiparticles for quite a while and they don't behave this way. There will indeed be some new particles with some anti-gravity like properties, but it's not simple antimatter.

      If you're interested in understanding this stuff, I highly recommend QED [amazon.com] by Richard Feynman. It's cheap, a quick read, and accessible to anyone who's interested and has a high school education. It's accurate enough to be used in graduate-level physics courses, but is complet

    • Antimatter is just like conventional matter, except for one (and only one) thing: the charges are reversed. E = mc**2 for it, just like for everything else in the universe. It has a positive mass, thus it has a positive energy level, thus it distorts spacetime in exactly the same way as matter.

      • E = mc**2 for [antimatter], just like for everything else in the universe.

        It was my understanding that the actual equation is E**2 = (m**2)(c**4) + (p**2)(c**2). For objects at rest, p = 0, and we get E = +/- mc**2.

        Given that, we have to accept the existence of a form of matter with either negative energy and positive mass, or positive energy and negative mass (or heck, both). I was always led to believe that antimatter was the latter, since when a particle and antiparticle collide, the result has no ma

        • I can understand how you could make that kind of mistake, however the error you made is making a distiction between matter and enery, when in fact, they're both the same. Matter is meerly another form of energy. When matter and anti-matter colide, they convert into what we call pure energy.

          But really energy and matter are the same stuff

  • Oh. It's not `dork matters`. D'oh! (Score:3, Funny)

    by AtariAmarok ( 451306 ) on Thursday August 07, 2003 @02:40PM (#6638295)
    I misread this at first, I thought it was some sort of reference to the Slashdot motto "news for nerds, stuff that matters". My mistake.

  • Judging from my single status.. (Score:3, Funny)

    by NanoGator ( 522640 ) on Thursday August 07, 2003 @03:02PM (#6638564) Homepage Journal
    ... I'd say that I'm the MASTER OF DARK ENERGY! Buaahaha

  • ...stuff like this goes and happens! I mean, GODDAMMIT I was just starting to get out the Universe worked but then....WHO ORDERED THAT!

    I've enjoyed reading about physics and cosmology since I was in high school, but just didn't have the math to actually pursue it. Now I'm glad I didn't...the more the physicists and astronomers investigate, the more they realize they haven't a clue what's going on!

    Maybe I'll go back to sleep and everything will be alright again...
    • Actually, to be fair, particle theorists have been saying for quite a while that there should be a cosmological constant, (This is what Dark Energy essentially is). Unfortunately, particle physics currently has this constant many, many orders of magnitude too high. Really the major thing about Dark Energy is it is a reversal of the previously widely held contention in cosmology that the universe was decelerating, but this is not the first time that cosmology has been reversed like this however with the ne
  • This sounds a lot more like a re-statement of the reason that people started theorizing that "dark energy" might exist. Confirmation? pfft.
    Mr. Hawk "We dont know why this is happening."
    Mr. Beard "Hmm,, maybe it's 'Dark Energy', that acts in reverse."
    Mr. Hawk "Hey look, the same thing is happening over here.. I wonder why.."
    Mr. Beard "This conclusively proves my earlier hypothesis!!"
  • We are finding that most of the stuff in our universe is abnormal ....
  • Firstly astronomers don't really have a valid explanation for Red Shift.
    Back in the 70's William G. Tifft noticed that the red shift of light is quantized [unc.edu]
    (there are heaps of other pages if you do a search [google.com])

    Based on this research, the red shift of light can't be based on velocity (as that would result in a smooth distribution of values, not discreet units). Therefore any assumptions about "dark" matter are based on an invalid assumption.

    I have my own theories about this quantisation, but I haven't gotte

  • I have always felt that gravitons would be found to be symmetrical - sounds like we are getting closer.

    I'm still waiting for my super-symmetrical beer.

    Q.

    • I wrote a book nearly 200 pages long on super-symmetrical umm... things!, you'd be surprized and terrified of what looking into "zero" could bring you. First off, imaginary numbers appear to look like zero. Ummmmm, what's the square root of imaginary? think of that for a start! -if you're interested. --Sonnie
  • I always thought that this was malarky, and now they're trying to shove it to us like its proof or something. Let's get this straight: until someone can harnest this 'dark energy' and prove to me it really exists, well, I'm not going to believe it. Instead I'm going to believe that gravity is a resultant factor of a lot of mass being in generally one place. Since I also theorize that matter is made of waves that are condensed into tangled balls of electromagnetic energy (sorry, no better definition for "
    • What do you think about a waveform particle accelerating to near the speed of light? It has been proven with atomic clocks that the faster something approaches the speed of light, the slower it's "clock_ticks" go. Could the speed of light just be an appearance of a "zero" in relativity to our own "frequency"?--in which as an object/waveform_particle approaches the speed of light, it's "frequency" decreases?, and that light it'self has no frequency,--it only appears to be having frequency due to it's appeara

  • Let's keep adding terms to the equations (Score:4, Informative)

    by nimblebrain ( 683478 ) on Friday August 08, 2003 @01:19AM (#6642731) Homepage Journal

    Now we've been decelerating...then accelerating?

    This is the thing that has been driving me absolutely crazy vis-a-vis the Big Bang theory, is that the practitioners seem to operate under the maxim:

    "Keep adding terms until the data fits"

    That's not the way science is supposed to work.

    We've had a fair share of juggling of terms, including:

    • "Big Crunch" - gravity will let the universe collapse again
    • "Flat Universe" - universe will expand forever, but keep slowing down
    • "Inflationary Universe" - universe expanded faster than the speed of light for a tiny moment (addressing the age and isotropy problems)
    • Not sure what to call this... "Second wind universe" - universe slows its acceleration before dark energy becomes the reigning cause of repulsion
    I sincerely doubt it will end there - the Missing Mass problem and the Age of the Universe problem [uiuc.edu] will push the equations incrementally.

    The Hubble telescope observations [hubblesite.org] are getting awfully close to the predicted age of the universe [nasa.gov]. I wonder what age-of-the-universe estimate this new theory will predict; something more than 13.7 billion years?

    The missing mass in the form of dark matter is, by all accounts, supposed to be mass that attracts; the inflationary universe theory depends on it for flatness. This might be another move 'around' the problem.

    The Big Bang theory fell from grace for me over a period of fifteen years. While I don't subscribe to the notions of Velan, I'm curious, yet ambivalent about Alfven's plasma cosmology [wikipedia.org], there are a number of viable cosmological theories that don't have age, mass or exotic physics problems. It seems we closed the book on alternatives too soon, and are constantly interpreting data so it fits with theory, instead of breaking the back of theory on data.

    Proving mathematically that you can never hit a wall [mathforum.org] must be tempered with observations of a hole in the wall and drunk in front of said wall on his back at a frat party :)

  • Actually, Mike, such a mechanism was proposed by George Lewis LeSage in 1784. The theory keeps on getting shot down, then revitalised in periodic cycles. There are those who have derived Newton's equations [mountainman.com.au] from this sort of paradigm, and there are those who have indicated that if gravitons (assuming such a particle is involved) go at the speed of light, there might be problems with orbits.

    I prefer to wait and see on the subject. I'm just waiting for the book Pushing Gravity: New Perspectives on Le Sage's [amazon.ca]

Slashdot Top Deals

Time is the most valuable thing a man can spend. -- Theophrastus

Close