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Fermilab Reports Dark Energy Not Needed

Posted by Hemos on from the like-inflation-in-gas-prices dept.

An anonymous reader writes "A Fermilab press release reports that the expansion of the universe may be explainable without the need for dark energy or a cosmological constant. Apparently, ripples from inflation in the early universe may account for the observed expansion rate of the universe."

35 of 416 comments (clear)

  1. Nothing for you to see here. by brilinux · · Score: 5, Funny
    Nothing for you to see here. Please move along.

    Well, apparently the dark matter is still important on Slashdot.

  2. But what about the Horizon problem? by mr100percent · · Score: 5, Interesting
    But what about the Horizon problem?

    From an earlier /.-linked article 13 things that do not make sense:

    The horizon problem

    OUR universe appears to be unfathomably uniform. Look across space from one edge of the visible universe to the other, and you'll see that the microwave background radiation filling the cosmos is at the same temperature everywhere. That may not seem surprising until you consider that the two edges are nearly 28 billion light years apart and our universe is only 14 billion years old.

    Nothing can travel faster than the speed of light, so there is no way heat radiation could have travelled between the two horizons to even out the hot and cold spots created in the big bang and leave the thermal equilibrium we see now.

    This "horizon problem" is a big headache for cosmologists, so big that they have come up with some pretty wild solutions. "Inflation", for example.

    You can solve the horizon problem by having the universe expand ultra-fast for a time, just after the big bang, blowing up by a factor of 1050 in 10-33 seconds. But is that just wishful thinking? "Inflation would be an explanation if it occurred," says University of Cambridge astronomer Martin Rees. The trouble is that no one knows what could have made that happen.

    So, in effect, inflation solves one mystery only to invoke another. A variation in the speed of light could also solve the horizon problem - but this too is impotent in the face of the question "why?" In scientific terms, the uniform temperature of the background radiation remains an anomaly.

    "A variation in the speed of light could solve the problem, but this too is impotent in the face of the question 'why?'"

    Also, in the same article, Dark Energy is discussed:
    9 Dark energy

    IT IS one of the most famous, and most embarrassing, problems in physics. In 1998, astronomers discovered that the universe is expanding at ever faster speeds. It's an effect still searching for a cause - until then, everyone thought the universe's expansion was slowing down after the big bang. "Theorists are still floundering around, looking for a sensible explanation," says cosmologist Katherine Freese of the University of Michigan, Ann Arbor. "We're all hoping that upcoming observations of supernovae, of clusters of galaxies and so on will give us more clues."

    One suggestion is that some property of empty space is responsible - cosmologists call it dark energy. But all attempts to pin it down have fallen woefully short. It's also possible that Einstein's theory of general relativity may need to be tweaked when applied to the very largest scales of the universe. "The field is still wide open," Freese says.

    1. Re:But what about the Horizon problem? by PureFiction · · Score: 5, Insightful
      If you read the article you would see they address this issue. The key is to realize that the horizon extends beyond what we can see (our cosmic horizon):
      • It is widely believed that during the inflationary expansion early in the history of the universe, very tiny ripples in spacetime were generated, as predicted by Einstein's theory of General Relativity. These ripples were stretched by the expansion of the universe and extend today far beyond our cosmic horizon, that is over a region much bigger than the observable universe, a distance of about 15 billion light years. In their current paper, the authors propose that it is the evolution of these cosmic ripples that increases the observed expansion of the universe and accounts for its acceleration.


      • "We realized that you simply need to add this new key ingredient, the ripples of spacetime generated during the epoch of inflation, to Einstein's General Relativity to explain why the universe is accelerating today," Riotto says. "It seems that the solution to the puzzle of acceleration involves the universe beyond our cosmic horizon. No mysterious dark energy is required."
    2. Re:But what about the Horizon problem? by niktemadur · · Score: 5, Funny

      While it is a generally accepted law that nothing WITHIN space can travel faster than light, this law may not apply to SPACE ITSELF, which could inflate at superluminous speeds if the correct conditions are present.

      I know this sounds bizarre, and I'm no expert on the subject, but I'll try to give a simple example that even I can understand:

      Let's say space is like a balloon.
      Matter are the molecules within that balloon.
      The matter within may not move faster than light by its' own means.
      But the balloon may inflate faster than light, and the matter within goes along for the ride.
      At the end of inflation, the matter has kept its' same relative position in space.

      The correct condition for inflation to happen is known as supercooling. Here is an example that Alan Guth used to describe it: water that's below 32 degrees farenheit but retains its' liquid state. However, just gently tap the plastic mold and the water will abruptly crystalize into ice before your very eyes. Supercooled water.

      Another example would be a beer in the freezer that's liquid, but turns to ice from the top down when you open the lid. Supercooled beer.

      Accordingly, the universe would have to inflate at a certain speed (much faster than light) to re-attain its' appropriate state under specific conditions.

      According to Alan Guth, most of the universe's matter cancelled itself out instants after the Big Bang, due to matter-antimatter collitions. In a super-excited state, the universe found itself almost empty, and had to readjust by inflation and a spontaneous burst of creation of matter. In fact, Guth said that with 28 pounds of matter under the right conditions, a universe just as massive as ours could be created. This is why Guth said that our universe could be the ultimate "free lunch".

      --
      Lil' Thindime, lilting a lacrimose lament, krashes the kwaint konfines of Kokonino Kounty
    3. Re:But what about the Horizon problem? by WaterBreath · · Score: 4, Interesting

      A few things:

      According to "accepted" theories of expansion, there is no epicenter. All space is expanding equally in all directions. So wherever you are standing, everything will appear to expand outward away from you.

      Because of that, things farther away from you will be receeding from you faster, because every extra bit of space between you and them means an extra bit of expansion, and so an extra bit of recession speed. As the theory goes, superluminal recession speeds are possible because the distant objects are not actually moving relative to the stationary frame of space in their vivinity. Space itself is changing shape, and the "motion" we see is just a side-effect.

      Supposedly, there is a certain distance, which can be measured starting at any given point, beyond which every everything is receeding from the reference point faster than light, and so will never be visible from that point. This is called the Hubble distance. Related is the Hubble constant, which is a measurement of change in velocity of expansion per unit distance from the reference point. (Not the odd way to measure acceleration. Normal acceleration is m/s/s, or m/s^2, but this is m/s/m, or just 1/s, which is 1Hz. Weird, eh?) The Hubble constant is under contention, I think, and the value of the Hubble distance depends on the value of the constant.

      Anyway, this stuff is kind of where the idea of Star Trek's "warp drive" comes from (at least in the more recent series). If it were possible to create some sort of device that could cause the space in front of a ship to contract and the space behind to expand proportionally, the ship could move without moving through space. It would be space itself changing shape around the ship that causes it to "move". And hence the speed at which you could move would be limited only by the speed at which you could channel energy into the expansion and contraction of space. Of course, this might just happen to be limited by the speed of light as well, so maybe superluminal speed still wouldn't be possible!

      But if these guys' new idea is right, then none of that matters. =)

  3. How did the ripples get there? by Dancin_Santa · · Score: 5, Insightful

    If there was nothing to push against, what would cause something to be held back and "ripple" as if there were some sort of repulsive force?

    Let's say we've reached the edge of the universe, what happens when we step beyond that boundary? What is out there that would possibly hold back further expansion of our universe?

    1. Re:How did the ripples get there? by TrekkieGod · · Score: 4, Informative
      If there was nothing to push against, what would cause something to be held back and "ripple" as if there were some sort of repulsive force?

      Not really related to the ripple they are talking about in the article, but "repulsive force" doesn't require something to push against. When students first learn of Newton's third law, "for every action, there's an opposite and equal reaction", teachers often give as an example that when you push against a wall, the wall pushes against you. That gives the idea to students that there must be something to push back against you (don't feel bad, some early rocket scientists thought the same thing). That is, however, not true. You don't need something to push against, you just need to exert a force in one direction, and there will be a a force in the opposite direction.

      Because of this misconception, it was originally thought that rockets wouldn't work in space, because the exhaust they put out wouldn't be able to push against the atmosphere. But hey, they do!

      Let's say we've reached the edge of the universe, what happens when we step beyond that boundary? What is out there that would possibly hold back further expansion of our universe?

      Gravity. There's an attractive force between every object with mass. When you jump, you move away from the center of the earth, but only for a short time. You accelerate up, but then you start decelerating. You reach a maximum height, then you start accelerating back down. During the big bang, the universe started expending. It was originally thought that there would be a "big crunch", and the universe would stop expanding, than start collapsing towards the center. Then we discovered the universe was not only not slowing down in it's expansion, but actually accelerating. That made no sense, so Dark Energy was used to explain it (a force like gravity, but pushing outwards). Under that scenario, the universe would end not through a big crunch, but would simply become dark as suns die and black holes evaporate. If we don't need Dark Energy, maybe the big crunch theory will come back.

      --

      Warning: Opinions known to be heavily biased.

    2. Re:How did the ripples get there? by Almost-Retired · · Score: 4, Informative

      Uhmm ... rockets work due to conservation of momentum, not because of some mysterious reaction force.

      Not a very good explanation. Rockets work in space because the exhaust gases are, in the process of being accelerated out the back of the engine, are pushing equally hard on the walls of the engine thats burning the fuel. Since thats cone shaped, wider at the rear, its the net circular square area of the back flange of the motor that the gasses push against, and its anchor to the rest of the rocket transfers that push to the rocket proper. And don't forget that a little like the e=mc2 of Einsteins famous equation, the net power, minus some losses here and there, is still e=mv2, so the holy chalice/grail of the rocket is the one that moves the gas at the highest velocity at the face of the nozzle, with some of the flame cone actually being a velocity to pressure translation so in the end, the gas velocity, being highest out near the tip of the flame, serves to increase the felt pressure pushing forward on the engine proper.

      The ion and plasma drives that use zenon gas, electrostaticly or thermally accelerated to a fraction of C speed, are many times more efficient in terms of the amount of push per pound of expendable than any chemically fired rocket can ever hope to be simply becasue of the 'fraction of C speed' is many times what a chemical fired gas generator can do.

      I've heard/read of estimates that a xenon gas rocket, fired by a nuclear light bulb heat source (circa 30,000 degrees C) making a plasma out of the gas, could go to Alpha Centari in just a few years, as it would accelerate at a steady .05G's to the halfway point, then turn around and decelerate at that same rate. THat of course means it would have to be launched into leo by some other means before lighting the torch. If not turned around and slowed down, it would go by Alpha Centari at truely relativistic speeds, near .99 C. I haven't personally ran the math, but the article I read 2 decades back sure did. ISTR the article said it would only take about 20 tons of gas. That was with estimates of about 5 tons for the whole nuclear light bulb reactor so the total vehicle weight wouldn't be near as heavy as a Saturn5 at launch. We played with such a reactor at Rocky Flats for a while, but the natives (thats us people folks) got restless. I don't know if there ever was a true 'accident' involving one of them because basicly if the 'light bulb' envelope fails, the reaction is self quenching. One of the safest reactors ever developed, but the word nuclear was its death knell.

      Sometimes I swear we are our own worst enemy.

      --
      Cheers, Gene
      "There are four boxes to be used in defense of liberty:
      soap, ballot, jury, and ammo. Please use in that order."
      -Ed Howdershelt (Author)
      99.34% setiathome rank, not too shabby for a WV hillbilly

  4. Inflation... by ackthpt · · Score: 5, Funny
    Apparently, ripples from inflation in the early universe may account for the observed expansion rate of the universe."

    Hmm. Better check the exchange rates on Altairian Dollars, Flainian Pobble Beads and the Triganic Pu.

    Has anyone contacted Alan Greenspan about this?

    --

    A feeling of having made the same mistake before: Deja Foobar
  5. Comment removed by account_deleted · · Score: 4, Informative

    Comment removed based on user account deletion

  6. Eddies in the space time continuum by starling · · Score: 4, Funny

    Arthur : Oh, is he?

  7. string theory Nova by Fox_1 · · Score: 4, Interesting

    Nova did a great piece on the all of physics (a lot on the universe and big focus on Quantum Mechanics and String Theory). It's pretty good if you are trying to find commonplace explanations of some of the theories the article just mentions and doesn't explain.

    --
    The rock, the vulture, and the chain
  8. Re:Space beyond the edge of Universe by ari_j · · Score: 4, Interesting

    Yes, there is space beyond the cosmic horizon. The horizon on Earth is just the farthest you can see because of the curvature of the planet's surface. The planet keeps going beyond the horizon - the horizon is a function of the observer. The same applies to the universe, although I am not knowledgeable enough to tell you if the cosmic horizon is the limit of what we can see because of the distance, because of a higher-dimensional curvature of the universe, or because of something else.

  9. WWDVS? by LokieLizzy · · Score: 5, Funny
    (What would Darth Vader say?)

    "Do not be so proud of this cosmological terror you have created. Its existence pales when compared to the power of the Dark Side."

    --
    My digital rights don't need management.
  10. I'm not an expert... by chazR · · Score: 4, Informative

    but Sean Carroll is. And he's not convinced.

  11. Gravity leaks by Tablizer · · Score: 5, Interesting

    I've read another hypothesis recently: that gravity slowly "leaks" into other dimensions so that over long distances it's attractive force diminishes, and that is why the universe is flying apart. The average distances between the galaxies has now reached a threashold where the leakage makes a big difference, giving the appearence of a relatively sudden expansion speedup.

    --
    Table-ized A.I.
    1. Re:Gravity leaks by XanC · · Score: 4, Interesting

      Even if gravity were zero, the universe would then expand at a constant rate. But it appears to be accelerating, implying some kind of negative gravity.

    2. Re:Gravity leaks by Stalyn · · Score: 4, Informative

      The hypothesis in question was explained here

      Also here for the braver souls.

      --
      The best education consists in immunizing people against systematic attempts at education. - Paul Feyerabend
  12. Re:Difference? by Pfhorrest · · Score: 5, Informative

    The other responses to this thus far are completely off. Dark matter and dark energy are not (by any current theory at least) related anything like how normal matter and energy relate via e=mc^2.

    Dark Matter is a hypothetical unknown "stuff" with normal mass just like regular matter but which we cannot observe with light; it doesn't appear to be emitting or noticably obscuring any kind of radiation. But we see the movement of galaxies in such a way that they appear to be responding to the mass of something that we can't see. Hence "dark matter" - we can't see it, but it seems to be some sort of matter. Think of it like leaves blowing in the wind - we can't see the wind, but we see the motion is causes.

    Dark Energy is another hypothetical unknown "stuff" that seems to be adding, somehow, to the velocity of all objects in the universe. It is postulated because the universe appears to be accelerating in its expansion, which does not make sense given an empty, neutral vaccum and a bunch of matter in it. It should be slowing down or at best, expanding at a steady rate. Hence "dark energy" - we can't detect it, but some source of energy which is causing the expansion of the universe to accelerate.

    Hope this helps.

    --
    -Forrest Cameranesi, Geek of all Trades
    "I am Sam. Sam I am. I do not like trolls, flames, or spam."
  13. Comment removed by account_deleted · · Score: 4, Insightful

    Comment removed based on user account deletion

  14. That Einstein... by Omniscientist · · Score: 5, Funny
    "Whether Einstein was right when he first introduced the cosmological constant, or whether he was right when he later refuted the idea will soon be tested by a new round of precision cosmological observations," Kolb said.

    So either way, Einstein was right. Damn you Einstein!!!

  15. Fermilab Reports Dark Energy Not Needed by secolactico · · Score: 4, Funny

    Fermilab Reports Dark Energy Not Needed

    Well, thank god! I was going crazy trying to find some.

    --
    No sig
  16. I believe in Dark Energy, and... by LokieLizzy · · Score: 5, Funny
    I'm not a scientist.

    But I did stay at a Holiday Inn last night. And when the lights went out at midnight (power outage), I can assure you that there was more than a little energy going on in the room next door.

    --
    My digital rights don't need management.
  17. Enjoy Fermilab's work while you can by stox · · Score: 5, Informative

    Their budget has been slashed almost in half. After all, low quality bombs are far more important than high quality science. In fact, spending on basic research is dropping at an alarming rate through all the national laboratories. This does not bode well for our future.

    --
    "To those who are overly cautious, everything is impossible. "
    1. Re:Enjoy Fermilab's work while you can by stox · · Score: 5, Insightful

      Well, we could get into a very long and detailed discussion into the value of basic research. I'll point out just a few of the benefits we have received from Fermilab, and leave the rest to you.

      1) Ever hear of a "computing farm"? I'm sure you have. The concept was pioneered at Fermilab.

      2) Ask Bob Young, "Who made the most important confirmation of the value of Linux in the early days?" Couldn't be Fermilab, could it? ( Bob Young was one of the founders of RedHat, BTW. )

      3) Who has done more basic research into superconductors? Who pioneered the use of superconductors? Fermilab.

      4) How many lives have been saved through the use of radiation for treating cancer? Neutron therapy was pioneered at Fermilab.

      5) Do you like American Buffalo? At one time, the only surviving herds were at Fermilab and Yellowstone. Fortunately, they have made a comeback.

      6) Enjoy using the web? Fermilab was the third website on the planet, behind CERN and SLAC.

      I'm sure I have missed a few, but I hope you get the point. We are lucky that our ancestors didn't take the same outlook as you. Some things need a horizon of lifetimes, not just your own. How long was the electron studied? Quantum theory? Radiation? Thankfully, many did, and have left us with a rich environment to live in. I hope the current generation, and those to follow, are wise enough to invest in the future with basic research.

      As for my assertion that money devoted to basic research is dropping at a alarming rate, I will leave this as an exercise for the reader. The results of your studies will be quite enlightening, and quite possibly, terrifying.

      --
      "To those who are overly cautious, everything is impossible. "
  18. Re:Not Funny, Insightful by wanerious · · Score: 5, Insightful
    Insightful? What would you like to have happen? Publish fewer articles? Not research it so much? Sheesh.

    This anti-intellectualism stain in /. responders is saddening. Basically it seems to be, "I don't understand what they're talking about, so I think I'll make fun of them" or "I don't understand the thousands of papers that have been published, so I'm going to shout something superior-sounding from the cheap seats". Dismissing a beautiful and maturing field of physics with "we don't really know anything, so give up" is a sophomoric and pretentious reaction.

    Sure, there's a bunch that we don't understand, but please realize that this is the way science works. Nature is too subtle for us to have canned and precise answers for her behavior. Cosmologists are rightly invigorated by the new data, and ought to be encouraged to research and refute each other's ideas.

  19. In other news... by sPaKr · · Score: 4, Funny

    The producers of Startrek Enterprise gave themselves concusions from repeated blows of their heads to their desks. One producer cried "Ripples in space time explain the universe, WHY COULDNT WE GET THESE GUYS AS WRITERS!'

    1. Re:In other news... by ari_j · · Score: 4, Funny

      How about

      COMES NOW the plaintiffs, who allege:

      1. Plaintiffs are producers of the TV show Star Trek: Enterprise.
      2. Defendants are the class of all scientists in the world.
      3. Defendants stole and used as their own a plot device from the Star Trek: Enterprise finale; namely the idea that ripples in space-time explain the universe.
      4. Because of defendants' act of plagiarism as described in paragraph 3, plaintiffs suffered gazillions of dollars of damages.

      WHEREFORE plaintiffs demand that the court give them gazillions of dollars from the scientists, and rename the universe "Space: The Final Frontier."

  20. What if Dark Energy Wasn't Required by nimblebrain · · Score: 4, Interesting

    There's a decent amount of evidence that has been mounting over the past few years that a large component of redshift is in fact intrinsic, i.e. not attributed to the Doppler effect.

    In some ways, it seems related to the much-glossed-over "K Effect" of a few decades ago, where it was found that bright, bright blue stars seemed to be systematically redshifted.

    Researchers like M. B. Bell are of the opinion that the intrinsic redshifts are superimposed on a Big Bang flow (reducing the actual velocity we should be measuring). Others, like Arp, believe that the Hubble Flow is an illusion, and that the universe is actually relatively static once you take away the intrinsic redshifts.

    David Russell's paper that just came out supports either view, and shows that other explanations (like Tully-Fisher Relationship errors or rotational velocities) are far too small to account for the large discrepancies.

    (Some more hubbub on the topic.)

    In either case, intrinsic redshifts will take a lot of pressure off researchers to find 'dark energy', because the discrepancies of speed/distance are much reduced.

    Then, perhaps, we can stop looking for something that isn't there? :)

    --
    Binary geeks can count to 1,023 on their fingers :)
    1. Re:What if Dark Energy Wasn't Required by TerrierTribe · · Score: 4, Informative

      oops, forgot the link: SCIAM.

  21. preprint by bcrowell · · Score: 4, Informative

    The preprint is here.

    --
    Find free books.
  22. Re:Why insist that the universe be "elegant"? by radtea · · Score: 4, Insightful


    It isn't the universe that has to be elegant, but our theory of it. The reason why is that we aren't very smart, and theories with fewer free parameters are a lot easier for us to understand.

    --Tom

    --
    Blasphemy is a human right. Blasphemophobia kills.
  23. Hear Hear by theolein · · Score: 4, Insightful

    Very well put! What really shocks me is that the cowboy mentality is even so prevalent here on slashdot, where many people interested in technology seem to believe that science is of no worth, but God and bombs are.

    I find it simply frightening, because I think it poses a very significant threat to the future of the USA, which is heading down the road of becoming a military power without the brains needed to steer it in a wise direction.

  24. Re:And they call me crazy? by dalyraptor · · Score: 5, Insightful

    No, something that does not appear possible or make sense in nature does not prove that god exists. You cannot put everything that you do not understand down to god, jesus christ!

  25. Re:And they call me crazy? by Glock27 · · Score: 4, Insightful
    Then along comes an argument like this. Gee we science types have data that all our science says doesn't make sense, so to explain it we'll postulate unexplained varying physical sates for the Universe that start for no reason we can nail down and then end for no particular reason we can give (Expansion), invisible energy that no one seems able to find (Dark Matter), or unprovable ripples that just happen to be beyond our ability to find or prove (Cosmic Irregularity Theory?). And our evidence for this? Well it makes our math look good (just as long as you use our equations to do the math with, anyway)

    What you're missing is that science has theories that make predictions about observable things in the real world.

    General Relativity, for instance, led to predictions of 1) longer particle decay times for moving subatomic particles, 2) different orbital period for Mercury than Newtonian mechanics predicted and 3) bending of starlight due to intervening gravitational fields. There are quite famous observations confirming these predictions.

    Similarly, there are quite convincing observations that lend support to the Big Bang theory. Cosmic backround radiation measurements, observed Hubble expansion and observations of galactic evolution as we look further away (further into the past) come to mind as examples.

    That is the difference between religion and science. Science attempts to verify its theories with observed phenomena and experiments. Religion accepts its theories based on blind faith.

    All that said, there is nothing incompatible between science and religion really, as long as your religion doesn't dogmatically insist its wisdom about the real world subsumes observed scientific knowledge (the big trap into which some Christian sects seem to have fallen). In fact, I would argue that quantum mechanics provides an interesting "out" for religion - quantum randomness versus "Gods will". After all, quantum randomness is neither knowable or predictable for us, but it might be exactly enacting Gods will...

    I've often wondered why Einstein said "God would never play dice with the Universe". Perhaps Gods dice are loaded. :-)

    --
    Galileo: "The Earth revolves around the Sun!"
    Score: -1 100% Flamebait