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Space Science

New Clues About the Nature of Dark Energy 166

Posted by michael from the spaced-out dept.
Jim Mansfield writes "With the Hubble space telescope no longer being serviced by NASA, it's good to see one of their hardest working and most famous satellites in the news again. According to their press release on the nature of dark energy, Einstein may have been right after all - and even if he turns out to have been wrong, it seems that dark energy is not going 'to cause an end to the universe any time soon' ... whew, that's a relief." See also a space.com story.
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New Clues About the Nature of Dark Energy More

New Clues About the Nature of Dark Energy

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  • I wouldn't worry (Score:5, Funny)

    by jeffkjo1 ( 663413 ) on Monday February 23, 2004 @09:40AM (#8361486) Homepage
    I wouldn't worry about the Hubble, it will just end up drifting off into space only to return 300 years later as H'ble, the super intelligent sentient telescope of the future, bent on destroying the human race.

    Ok, so maybe there is reason to worry....

    • Ok, so maybe there is reason to worry....

      Naah... because by then there will be a crew of people who a few years previously will have saved the world once a week for 26 weeks out of the year. We'll be in good hands.

      -Rob

    • Re:I wouldn't worry (Score:4, Funny)

      by DangerSteel ( 749051 ) on Monday February 23, 2004 @10:16AM (#8361675)
      Is that why we will have to go back in time to get a whale to talk to the evil telescope... no.. wait.... we will have to explain to it why we decided not to repair the telescope and give it an extended life.....dammit, I'm all confused now...
    • "I wouldn't worry about the Hubble, it will just end up drifting off into space"

      Actually, NASA would likely send up a robotic mission to safely take it down over an ocean.

      Also, Hubble isn't written off yet -- there's still a chance [hubblesite.org] that a shuttle might service it.

  • To say the dark side of the force is much much more powerful than the light.

    The Sith Lord awaits.

  • The restaurant at the end of the universe (Score:4, Funny)

    by dapyx ( 665882 ) on Monday February 23, 2004 @09:47AM (#8361524) Homepage
    ..dark energy probably won't destroy the universe any sooner than about 30 billion years from now, say Hubble researchers.

    The restaurant at the end of the universe must be really far...

  • Racists! (Score:2, Funny)

    by dapyx ( 665882 )
    the dark energy probably won't destroy the universe any sooner than about 30 billion years These damned white scientists are racists: yesterday they said that a black hole destroyed a star, now this: the dark energy will destroy our universe!

  • ...End of time? (Score:5, Interesting)

    by nharmon ( 97591 ) on Monday February 23, 2004 @09:53AM (#8361560)
    If the repulsion from dark energy is or becomes stronger than Einstein's prediction, the universe may be torn apart by a future "Big Rip," during which the universe expands so violenty that first the galaxies, then the stars, then planets, and finally atoms come unglued in a catastrophic end of time.

    This is quite a shift from the implosion theory that results in pre-'Big Bang' conditions causing a loop in time.

    • Re:...End of time? (Score:5, Interesting)

      by sbma44 ( 694130 ) on Monday February 23, 2004 @10:00AM (#8361588)
      Yeah, but that theory's been out of vogue for a while. It's theoretically tidy (and therefore attractive), but I believe the last few years' astronomical data has shown the universe's rate of expansion is accelerating. Something new woulkd have to turn up for the Big Crunch to come into vogue again.

      • Re:...End of time? (Score:3, Interesting)

        by SashaM ( 520334 )
        I always wonder whether the "It's accelerating so it'll drift apart in the end" folks understand basic calculus. The rate of expansion accelerating doesn't mean it will continue accelerating - the third derivative of x(t) could be negative, or the fourth, and then the fifth could be positive again. You need to know all of the derivatives to know the function itself (and even that isn't true for some functions - e^(-1/x^2) IIRC).

        • Re:...End of time? (Score:5, Informative)

          by V_M_Smith ( 186361 ) on Monday February 23, 2004 @11:51AM (#8362450)
          I always wonder whether the "It's accelerating so it'll drift apart in the end" folks understand basic calculus. The rate of expansion accelerating doesn't mean it will continue accelerating


          Well, if you've done any General Relativity you'll know that for a standard cosmology (FLRW cosmology), the final state is one of recollapse, asymptotic expansion, or accelerating expansion. This end state depends on the total mass-energy content of the universe and the nature of the dark energy (cosmological constant). It really isn't a lack of understanding of "basic calculus", but rather a deeper understanding of the physics involved. So, basically, we don't need to know all the derivatives -- we just need to have an understanding of the potential in which our universe evolves.

        • Re:...End of time? (Score:5, Informative)

          by Bootsy Collins ( 549938 ) on Monday February 23, 2004 @11:58AM (#8362507)

          Of course they understand basic calculus. They just also understand the currently prevailing model for the constitution of the universe and its evolution. To have the accelerating expansion stop accelerating, decelerate, or turn over would require some additional, extremely bizarre physics that's not indicated by any observation or experiment we presently have. This may seem like an odd constraint for me to place when we're talking about something as bizarre as "dark energy", but it isn't. There were a lot of theoretical reasons from both cosmology and elementary particle physics (and even a few vague extragalactic observational reasons) to at least consider that the cosmological constant may be nonzero; that's why the two high-z supernova teams did their work. And now there's still harder data suggesting same. In contrast, there's just no reason whatsoever to presume unbelievably bizarre physics of the form necessary to produce the behavior to which you appeal. The scale-factor dependence of the currently-known components of the Universe don't have the higher-order derivative behavior you appeal to; while coming up with a hypothetical field that does is pretty damned hard. That doesn't mean you're wrong, of course; it just means the odds are very highly against you. The claims they're making are almost certainly true.

        • Re:...End of time? (Score:2, Interesting)

          by Anonymous Coward
          In a Friedmann-Lemaitre cosmology, if the universe is dominated by mass, then the rate of expansion cannot accelerate.

          This is why the observation of an accelerating rate of expansion (first convincingly made in 1998) indicates that there is something other than mass... and that something, whatever it is, in fact dominates the evolution of the universe at the moment.

          As for whether the universe drifts apart in the end... you are right that this is a strong prediction. But it is at least a feature of a fair

        • Re:...End of time? (Score:5, Insightful)

          by egomaniac ( 105476 ) on Monday February 23, 2004 @02:29PM (#8364177) Homepage
          I always wonder whether the "It's accelerating so it'll drift apart in the end" folks understand basic calculus.

          You always wonder whether astrophysicists understand basic calculus?

          I'm doing my best to come up with something witty or intelligent to say to that, but I'm having trouble coming up with anything more than "What...? Huh?"

          Considering that modern physics is largely just a whole hell of a lot of math, yes, I think it's safe to say that astrophysicists understand the principles of calculus. Have you even seen a modern physics paper?

      • Big Rip a Big improbability (Score:5, Informative)

        by Pi_0's don't shower ( 741216 ) <ethan&isp,northwestern,edu> on Monday February 23, 2004 @10:52AM (#8361956) Homepage Journal
        If you fear things involving physics, skip the rest of this post. Alright, for those who are interested, it seems like 70% of the current energy density of the universe is in some form of "dark energy", as was previously stated. The Universe is currently 13.7 billion years old. We say that every component in the universe has an energy density and a pressure. Dark energy is different from things like normal matter and light, because these have positive pressures. (Normal matter has a very small pressure). But dark energy has a negative pressure, which means it works opposite to gravity. Everything that has a pressure that we can physically think of (well, that I can physically think of) has a pressure between (-1)*energy density and (+1)*energy density. A big rip will only occur (and it will only occur in the very distant future) if the dark energy has a pressure that is outside this range, such that pressure is less than (-1)*energy density. This is, of course, possible, but unlikely in my view.

    • Not with a whimper, but a "Big Rip"? (Score:3, Funny)

      by Anonymous Coward
      "And in the end of days, God shall eat Mexican food and several beers and ye verily shall His mighty thunder rend the Heavens."
  • Poor, poor huble. Getting scrapped by Nasa. You can just see he's getting really depressed. He already has a black outlook on life, all that dark energy...

    Well, it's his own fault now, giving us back such negative waves [the-ocean.com].

    Reinout

  • Never underestimate the power of the schwartz! (Score:3, Funny)

    by mikeophile ( 647318 ) on Monday February 23, 2004 @09:54AM (#8361563)
    Oh sorry, I thought the headline was New Clues About the Nature of Dark Helmet.

    "Now you see that evil will always triumph, because good is dumb!"

    - Dark Helmet

  • The future of the Unvierse (Score:4, Interesting)

    by Neuropol ( 665537 ) on Monday February 23, 2004 @09:56AM (#8361571) Homepage
    After we have all (I assume that doesn't include any creationsists) adhered to the scientific theory of The Big Bang and the beginning of the Universe as we know it, I can only think that we can begin to accept the fate of the Universe.

    As dark matter destabalizes, essentially matter is pulled apart at the atomic level. Some thing tells me The Big Rip, is what we are in for.

    The universal constant is a nice theory and would be the better, happily-ever-after option, but in reality it seems a little far fetched if the expansion of the Universe is accelerating. It means that eventually speed will over come matter and every thing disintegrate and get ripped apart.

    • Big Rip != Acceleration (Score:5, Informative)

      by jpflip ( 670957 ) on Monday February 23, 2004 @11:28AM (#8362279)
      The fact that the universe is accelerating is not the same as the "big rip". The accelerating universe, as we understand it now, sort of means that the space between everything and everything else is getting bigger all the time. However, in order to discover this (and the expansion of the universe in general), we have to look at very distant galaxies - we don't see our own galaxy flying apart, and some other galaxies bound together in our local galaxy cluster are orbiting or moving toward ours. In general, objects that are in bound states - whether gravitational bound states (like solar systems and galaxies) or other bound states (atoms, etc.) will remain held together even as the distant galaxies which are not tightly bound to us zoom away. Our own situation on earth would be completely unaffected - you'd need a big telescope to even tell the difference. The idea of the "Big Rip" is that this condition that "bound things stay bound" (the dominant energy condition) might be violated, that dark energy might be so extreme that not even bound objects could keep from eventually dissipating. That idea is HIGHLY theoretical - there's no particular evidence for it, and until recently most theorists thought it was ridiculous. But, of course, this is science - we have to think about even the weird possibilities.

  • Relief? (Score:5, Interesting)

    by philbert26 ( 705644 ) on Monday February 23, 2004 @09:58AM (#8361579)
    If a big crunch doesn't end the universe, then heat death will. Eventually the universe will reach a state of maximum entropy, and nothing interesting will happen.

    Before it gets to that stage, stars will become a rare occurance. The chain of star birth and death results in smaller stars, and once stars get small enough they become like our Sun -- too small to undergo the explosive death that would provide enough mass for future stars. Eventually there won't be enough clouds of hydrogen massive enough to start nuclear fusion.

    Given enough time, current theories suggest that the universe seems to be screwed either way.

    • current theories suggest that the universe seems to be screwed either way.

      Reminds me of a Futurama episode.. the universe has just been destroyed by a time paradox, but oddly enough the main characters find themselves alive, floating around in white nothingness.

      Some guy: Where are we?!
      Al Gore (playing as himself): Well, I can tell you where we are not; THE UNIVERSE!!

    • Re:Relief? (Score:2, Interesting)

      by thelasttemptation ( 703311 )
      Tho what's to say that we won't have the tech to scoop up the matter and make our own stars? Maybe the universe counts on intelligent life to keep it going?

    • Re:Relief? (Score:2, Insightful)

      by Gr8Apes ( 679165 )

      1) I seem to recall there's no such thing as maximum entropy. There's just the law that for any closed system, entropy never decreases. (Third law of Thermo? It's been waay too long ago...;)

      2) The eventual cold death/ever expanding argument. I think they're still trying to figure out which way the universe is going to go.

      If only the universe were as simple as E=mc2

    • Re:Relief? (Score:3, Interesting)

      by sploxx ( 622853 )
      Being a physics student, I really don't understand the heat death argument. The heat death argument relies on the 2nd law of thermodynamics -i.e. there can't be an entropy loss. But this is not exactly true. It is unbelievable improbable that an entropy loss occurs. If one supposes that time goes one after a heat death, there can and will be a restructuring(*) of the universe. The probability that a restructuring happens is unbelievable small. But as time approaches infinity, the probability that this hap
      • I'm not a physicist either, but just looking at this from a simple perspective, if heat death occurs, and everything is slowly approaching 0 degrees kelvin, isn't the concept of time fading as well? Once everything comes to a halt and nothing is happening, then time becomes a frivolous dimension anyway.

        It's sort of as though the "time" dimension itself will be curling up to insignificance the same way we currently understand higher spatial dimensions to be curled up...

      • Re:Relief? (Score:5, Interesting)

        by xigxag ( 167441 ) on Monday February 23, 2004 @11:48AM (#8362429)
        It's true that entropy can decrease when matter/energy enters a spontaneously ordered state, e.g. all the gas collects in the corner of the room. In itself that's infinitesimally unlikely, yet still possible. But in the case of the universe we live in, there's an additional wrinke. The edges of the "room" are expanding faster than the speed of light. Which means, eventually, every particle will disappear over every other particle's event horizon, and it will be impossible to put them back together again.

        Another person downthread alludes to the idea of surviving through increasing entropy by presumably using decreasing amounts of energy. In other words, as the universe gets older and colder, there will be, say, 1/100th the free energy available utilizable by a heat pump. So a form of alife could simply run itself 100 times more slowly and thereby experience time subjectively at a linear rate. Right? Wrong. Two problems pop up. One is proton decay, which means the building blocks of any sentient computer will eventually decay on their own. And second is the cosmic background radiation. Machines work on the principle of taking in energy and outputting it in the form of waste heat. But once the universe has cooled down to the same temperature as the CBR, it will be impossible for any machine to output waste heat. It will cease to function. There is some work being done on reversible computing [mit.edu] which might, in the long run, be able to tackle the second problem, but not the first.

        • Re:Relief? (Score:3, Interesting)

          by naasking ( 94116 )
          Machines work on the principle of taking in energy and outputting it in the form of waste heat.

          Machines work on the principle of energy conversion; waste heat is just an unwanted side effect of imperfect energy conversion.

          But once the universe has cooled down to the same temperature as the CBR, it will be impossible for any machine to output waste heat.

          Once the universe cools to CBR levels, there will be no differences in energy levels, and thus no energy flow is possible (thus, no motion, no conversi

        • Re:Relief? (Score:3, Interesting)

          by barawn ( 25691 )
          One is proton decay, which means the building blocks of any sentient computer will eventually decay on their own.

          You do realize that no one has seen one proton decay. Not one, right? Proton decay assumes supersymmetry is valid, and as many physicists have noted, supersymmetry is an excellent theory, which predicts a whole host of particles - half of which have been discovered.

          Proton decay isn't real - not yet. And there is no a priori reason to assume that it is. Its current lower bound is 10^33 or so ye

      • The heat death argument relies on the 2nd law of thermodynamics -i.e. there can't be an entropy loss. But this is not exactly true. It is unbelievable improbable that an entropy loss occurs. If one supposes that time goes one after a heat death, there can and will be a restructuring(*) of the universe. The probability that a restructuring happens is unbelievable small. But as time approaches infinity, the probability that this happens will approach one.

        Such an argument would only hold if that unbelieva

    • Re:Relief? (Score:5, Informative)

      by Psiren ( 6145 ) on Monday February 23, 2004 @10:28AM (#8361771)
      Stephen Baxter (I think?) wrote a very good book (Time) based around the idea of heat death. Some of the ideas that civilzations come up with to make the most out the last remaining energy in the universe is very neat. Well worth a read.

  • non-physical physics (Score:5, Interesting)

    by Space cowboy ( 13680 ) on Monday February 23, 2004 @09:59AM (#8361585) Journal
    Right now we're about twice as confident than before that Einstein's cosmological constant is real,


    Of course, 2x (near-as-dammit-zero-certainty) is pretty much the same as (near-as-dammit-zero-certainty)...

    A lot of new physics does seem to be increasingly theoretical and "out there" on the proverbial limb. It would be good for the practical lot to catch up with the theoretical lot... unfortunately, trying to verify these out-there hypotheses seems to involve larger and larger atom-smashing accelerators. Lets just hope they don't need to find the 'Higgs Boson' (hint: ohhh WAAAY ohhh, ummm barrray :-)

    Simon

    • Re:non-physical physics (Score:4, Insightful)

      by poindextrose ( 640377 ) <slideruleNO@SPAMgmail.com> on Monday February 23, 2004 @10:15AM (#8361670) Homepage
      A lot of new physics does seem to be increasingly theoretical and "out there" on the proverbial limb


      All new physics is out on the proverbial limb. Galileo's ideas were so outrageous at the time that the church had him outcast from society (IIRC).

      It doesn't take that much of an open mind to consider these new (or old) theories based on new facts. But, I'm glad the majority don't follow such theories, because most people tend not to leave things in the grey ("THIS theory is RIGHT") otherwise, actual scientific progress would be severely hindered, as people would become quite disheartened, and possibly ANGRY at science.

      It would be good for the practical lot to catch up with the theoretical lot...


      The border between "Practical" and "Theoretical" isn't very black-and-white either. Often theoretical sceince leads to very practical applications (as in the case of forward error correction, originally just mathematics) and practical turns out quite sour (as in the Wankel(?) engine).

      Just my 2c

    • Understanding dark energy and determining the universe's ultimate fate will require further observations.

      I'd say this is a bit flimsier limb to stand on. For a bit of perspective, let's consider the sheer mountains of daily empirical data that a meteorologist has to work with, and yet the "ultimate fate" of weather can rarely be predicted more than a few days in advance.

      Of course the size of the system does come into play, and the scope of the effects being observed. It may be far easier to understan

    • (hint: ohhh WAAAY ohhh, ummm barrray :-)
      I think you mean: vayo a-o, a home va ya ray, vayo a-rah, jerhum brunnen g [myrealm.co.uk].
    • There are two types of out there physics. The type that can be proven to not be true by observation, and those that can't be proven to not be true by observation. Which is a little different from being shown to be close enough to reality. The former go away and the later continue to provide us many hours of speculative enjoyment. The common feature of all of these is that they solve some theoretical problem. Fortunately solving some theoretical problem is not enough and the theories tend to languish un
      • Planck looked the black body radiation problem and the ultraviolet catastrophe and sent of a postcard claiming that fatal flaw was the assumption that energy was continuous.

        Actually, according to Kuhn [amazon.com] (and I tend to agree), Planck actually didn't realize he was making that break from classical physics.

        Planck had worked on the black-body problem for a long time, and only after that time did he cave in to follow Boltzmann's ideas, thinking at the time that the quantization condition was simply a mathematic

  • Dark Matter and Ether (Score:3, Insightful)

    by GerritHoll ( 70088 ) <gerrit@nl.linux.org> on Monday February 23, 2004 @10:00AM (#8361586) Homepage
    I find it strange that scientists 'believe' in dark matter. The main reason for the hypothesis that dark matter exists, is that otherwise those huge systems of galaxies don't obey Newton's laws. However, throughout the 20th century, there have been numerous occasions where Newton either was proven wrong or where fields of science were found where his laws weren't applicable: ether didn't exist, at nanoscale Newton's laws don't apply (quantum mechanics), at very high velocities they don't either (relativity), and in very complex systems Newton can't be used (chaos). Why would it be so strange if systems with enormous scales and very small accelarations would not obey Newton's laws? It does feel a bit like Ether to me to introduce a form of matter/energy which has never been measured at all...

    I think dark matter doesn't exist. It can be useful in the models, like ether could, but nothing more than that.

    • Re:Dark Matter and Ether (Score:5, Interesting)

      by Aardpig ( 622459 ) on Monday February 23, 2004 @10:10AM (#8361647)

      and in very complex systems Newton can't be used (chaos)

      Hang on a moment; I thought the Lorenz attractor (which is the canonical example of chaos) was based on a system obeying Newtonian mechanics.

      Why would it be so strange if systems with enormous scales and very small accelarations would not obey Newton's laws?

      This is the line of thinking which led Mordechai Milgrom to propose Modified Newtonian Dynamics (MOND) in the 1980s. MOND posits that Newtons second law (F=ma) is modified when the acceleration is very small. It is able to "explain" the unusual rotation curves of galaxies, without the need to invoke dark matter. It can also explain phenomena which the dark matter hypothesis can't, such as the Tully-Fisher relationship observed in the surface brightness of galaxies.

      However, its important to remember that MOND cannot be considered a physical theory; it is more of an empirical modification of known physical laws (like the Lorentz transformation was), which still awaits a physical explaination.

      • Re:Dark Matter and Ether (Score:4, Informative)

        by barawn ( 25691 ) on Monday February 23, 2004 @11:10AM (#8362092) Homepage
        It can also explain phenomena which the dark matter hypothesis can't, such as the Tully-Fisher relationship observed in the surface brightness of galaxies.

        The Tully-Fisher relation has been explained by dark matter for some time. You can find a brief derivation in Carroll & Ostlie p. 1002, for instance. There's no need to invoke MOND at all - it just comes from the fact that the luminosity is proportional to the maximum velocity to the 4th power, which you can get by using the expression for total mass contained within the galaxy derived from rotational velocity curves.

        • There's no need to invoke MOND at all - it just comes from the fact that the luminosity is proportional to the maximum velocity to the 4th power, which you can get by using the expression for total mass contained within the galaxy derived from rotational velocity curves.

          I was under the impression that dark matter needs fine tuning to explain Tully-Fisher, while MOND needs no further parametric adjustment beyond that used to fit rotation curves. That is the point I was (poorly) trying to make.

          • Re:Dark Matter and Ether (Score:5, Informative)

            by barawn ( 25691 ) on Monday February 23, 2004 @02:19PM (#8364048) Homepage
            I was under the impression that dark matter needs fine tuning to explain Tully-Fisher

            Yes and no: The typical Tully-Fisher coefficients for Sa, Sb, and Sc type galaxies are 9.95, 10.2, and 11.0 or so. These are all within 10%, and for Sa and Sb types, within 5%, of 10. Simple assumptions get you a coefficient of 10, if you assume that the mass-to-light ratio is the same for all spirals, and that the surface brightness is the same for all spirals.

            The first assumption (mass-to-light ratio) is a clearly idiotic assumption. It assumes that galaxies form with same proportions of light and dark matter, which we *know* is not true for other types of galaxies (dwarf ellipticals, in particular). Aside: This is also the "nail in MOND's coffin", more or less - MOND was hoping to replace the dark matter hypothesis by saying physics works differently at large distances. The problem is that galaxies which contain the same amount of light-emitting matter and have the same spatial extent should therefore have the same rotation curves. This isn't true. You then have to add a new parameter with MOND to fit it, which is OK, sure, but now you've started to lose the elegance originally intended, and now MOND becomes a more complicated theory than the dark matter hypothesis, which just says "well, that galaxy formed around less dark matter."

            Anyway, back to the subject: the point is that those two assumptions clearly are not completely true, and therefore there's plenty of room for a 10% correction due to forming biases in spiral galaxy types. If the mass-to-light ratio is a very weak function of mass (which is believable - perhaps smaller galaxies formed when the dark matter density was slightly lower, due to their late formation times), you can easily get those corrections.

            MOND allows you to get that 10% correction due to the parametric fit of the rotation curve, which is essentially identical to the way that it's done in the dark matter case - the corrections are due to the variation in the rotation curve, which MOND says is due to a modified Newtonian field, and dark matter says is due to a dark matter density. It's the same reasoning - one isn't more natural than the other.

            (It should also be noted that the Tully-Fisher data has a crapload of spread to it, just like all astronomical data. Each galaxy varies a fair amount.)

      • Hang on a moment; I thought the Lorenz attractor (which is the canonical example of chaos) was based on a system obeying Newtonian mechanics.

        Perhaps it would be better so say that Newton's laws make no meaningful predictions in such a situation, or at least, they don't converge nicely.

    • Oh man... where to begin.

      You say they 'believe', then call it a hypothesis - one is faith the other is science.

      "otherwise those huge systems of galaxies don't obey Newton's laws" - As the story notes, the proposed dark matter is related to Einstein's cosmological constant. Now as to why Einstein 'believed'(sic) in it? Because that is what observation showed. The question here is why and is it truly constant.

      "It does feel a bit like Ether to me to introduce a form of matter/energy which has never been

      • I think it is very well possible to believe in a hypothesis. There is a thin line between hypothesis and theory. It's possible to believe in a theory. Evolution is a theory. I think evolution is a fact, and that means I believe this theory is true. It can be dangerous to believe in a hypothesis, because it may mean closing they eyes for alternatives. I am not saying this is happening with dark matter, but it happened in the past, happens in the present and will happen in the future - just because scientists
        • Nah, disagree completely. It is semantic hair splitting though... Belief has no place in science - only confidence. Belief in a possibility (ie. theory/hypothesis) is an obvious oxymoron.

          Q.

    • we're well out of the Big Bang, there's quite a difference.

    • Re:Dark Matter and Ether (Score:5, Informative)

      by snake_dad ( 311844 ) on Monday February 23, 2004 @10:34AM (#8361814) Homepage Journal
      The article is about dark energy, not dark matter. Those are two distinctly different things. Dark matter is simply matter that has not been found, but that astronomers assume must exist to explain certain gravitational behaviour as observed in galaxies. AFAIK there is not much controversy over wether dark matter is real or not. Dark energy however is theorized to be a force that acts opposite to gravity, and that could explain why the rate of expansion of the universe seems to be increasing.

      IANA astronomer, but that's what I've understood from the stuff that I've read about it. Pop science ofcourse because the math is way over my head.

    • I find it strange that scientists 'believe' in dark matter. ... I think dark matter doesn't exist.

      Dark matter does not necessarily mean exotic matter. There have already been detections [space.com] of white dwarf stars at the edges of a galaxy. These are just very very dim stars. This discovery means that a significant part of the mass attributed to dark matter could be ordinary matter in dead stars that are no longer radiating at currently detectable levels.

    • There's more to dark matter... (Score:4, Informative)

      by jpflip ( 670957 ) on Monday February 23, 2004 @11:42AM (#8362389)
      You're right, the natural step when we learn that the universe doesn't obey Newton's laws should be to try to modify Newton's laws, not to imagine that there is a magic 95% of the universe with funny unobserved properties. The thing is that this isn't the only evidence for dark matter. There are a number of different lines of evidence which lead to the same conclusion - the orbital behaviors of galaxies and their clusters, the adundances of various light elements in the universe, the behavior of the cosmic microwave background, x-ray emission from clusters, etc. It turns out that no matter how hard we try, we can't modify Newton's laws to get the right answer to all of these. Gravitational lensing (the bending of light by the mass of distant galaxies and clusters) is really impressive in this regard - modifying Newton's laws (and general relativity) in the desired ways should have essentially no effect on it, and it definitely looks like there's dark matter (and even allows us to map its distribution). Dark matter really seems like the SIMPLEST answer, from the point of view of someone who knows the data! Dark energy was the subject of the article, however, and that's quite a bit different. As of right now, I'd say that we DON'T have very convincing evidence that this isn't just a modification of general relativity. All of our particle physics-related ideas seem far too complicated. Oh, and chaotic systems still obey the laws of classical physics - the systems are just so complicated that knowing how the individual atoms are behaving is not very helpful for predicting the behavior of the macroscopic system.

    • Re:Dark Matter and Ether (Score:3, Interesting)

      by kisak ( 524062 )

      First of all Newton was not proven wrong by quantum mechanics and the general relativity, in a way Newton's law has been put on a more secure footing by being supported by these two breakthroughs of modern physics. Sure, modern physics understands that Newton's laws don't apply for high velocities (close to the speed of light, c) and very small systems (when Planck's constant h becomes a siginificant number). But both quantum mechanics and general relativity gives you Newton's equations when c = infinity an

  • But the "Cosmological Constant" Einstein was credited for theorizing on was Ether, and eventually disproved the existance of Ether himself by somehow using the earths revolution around the sun.

    While this may be a completely seperate idea, it definitely appears that the author is mixing these two (Dark Energy and Ether) Einstein theories.
    • Prior to Kepler, scientists believed their was a planet Vulcan that shared Earth's orbit but the two were 180 degrees apart. Vulcan had the same mass as Earth and without the planet, scientists couldn't fit Earth's orbit into the Law of Universal Gravity.
      • Sorry but the parent post is NOT Insightful; it's utterly confused. Firstly, Vulcan was a hypothetical planet [unmuseum.org] in between the Sun and Mercury, proposed in the 19th century order to explain the advance of Mercury's perihelion (which was later accomplished by general relativity). Some observations were claimed in the 19th century but never verified and we know now that it was bogus.

        The thing you seem to be thinking of is the unseen antichthon or counter-Earth [wikipedia.org]; this dates from classical Greece where it was an

    • Re:Correct me if I'm wrong (Score:5, Informative)

      by GammaRay Rob ( 452271 ) on Monday February 23, 2004 @10:18AM (#8361684)
      You're wrong. Aether was thought to be a physical fluid whose ripples were the basis of the wave-like nature of light. This was proven not to be so by Michelson and Morely, who showed that the speed of light was the same no matter if it were going with or against the aether (which was presumably flowing past the moving Earth). Dark energy is a field, like light or gravity, which presumably has no preferred frame of reference (like light or gravity).

  • It seems this "dark energy" is quicker, easier and more seductive.

    I'd buy that for a dollar!

  • Everything's nonsense (Score:1, Funny)

    by Anonymous Coward
    The end of the unverse makes me depressive. Nothing that is eternal. No sense in building up things, inventing, scientific discoveries and everything. Just nonsense. Well, if you do not believe in god or are at least agnostic.

    Well, back to my OSS/FS projects to gain fame in this dark world :)
  • .. it's full of Goths! I hereby dub the matter 'Mopotronium
  • It's like regular matter, only it has a goatee. I thank yew.

  • Einstein was wrong anyway (Score:5, Insightful)

    by KjetilK ( 186133 ) <kjetil AT kjernsmo DOT net> on Monday February 23, 2004 @10:20AM (#8361696) Homepage Journal
    It wasn't the introduction of the cosmological constant per se that Einstein thought of as his greatest blunder, it was the failure to realize and predict that the Universe is expanding. The cosmological constant he had there to get a static universe, and that's bad. Also, the cosmological constant isn't Evil, it comes rather naturally from solving the equations. I never got as far as actually doing that, but I followed a back-of-envelope solution once, and it comes out sort of like an integration constant. I think of it as a natural parameter that should be constrained by observations just like any other parameter, and I see no particular reason why it should be 0.

    • Re:Einstein was wrong anyway (Score:4, Informative)

      by khallow ( 566160 ) on Monday February 23, 2004 @10:49AM (#8361927)
      Actually, the cosmological constant can result in an expanding universe.
      • Yep. Actually, the cosmological constant can result in many funny forms of universes, including my favorite "bouncing universe", which, sadly, is now pretty solidly rejected by observations. :-)
      • Actually, the cosmological constant can result in an expanding universe.

        Ok, while that picked up +4 informative, it wasn't really informative. The cosmological constant actually can be used in general relativity models to regulate the rate at which expansion or contraction occurs.

        The idea is that, if the vacuum inherently has a positive or negative curvature, then your cosmological model has a cosmological constant. Hence, it has a nontrivial contraction or expansion (positive or negative curvature re

    • Re:Einstein was wrong anyway (Score:4, Interesting)

      by GMFTatsujin ( 239569 ) on Monday February 23, 2004 @11:43AM (#8362392) Homepage
      This whole "Eistein was right after all" angle is misinformed. He wanted a static universe because that was the historic conception of the universe. His own science didn't allow for it, but he wrangled an equation for one out of it anyway. Turns out he was wrong, is wrong, and will always have been wrong. Einstein's motivation for putting in the cosmological constant was ideological, not observational -- and that's a recipe for Dumb Science.

      Dumb Science isn't "right after all," no matter how much you respect the guy who came up with it.
      • This whole "Eistein was right after all" angle is misinformed. He wanted a static universe because that was the historic conception of the universe. His own science didn't allow for it, but he wrangled an equation for one out of it anyway. Turns out he was wrong, is wrong, and will always have been wrong. Einstein's motivation for putting in the cosmological constant was ideological, not observational -- and that's a recipe for Dumb Science.

        Not exactly. Einstein didn't "put in" the cosmological constant;

      • Re: Einstein was wrong anyway (Score:5, Insightful)

        by Black Parrot ( 19622 ) on Monday February 23, 2004 @01:01PM (#8363057)


        > This whole "Eistein was right after all" angle is misinformed. He wanted a static universe because that was the historic conception of the universe. His own science didn't allow for it, but he wrangled an equation for one out of it anyway.

        Remember that at the time Einstein introduced it (1917, if a Web search didn't lead me astray) scientists still thought "the universe" and "the galaxy" were the same thing. We tend to forget how vastly our understanding of the universe has changed in the past ~80 years.

      • Why is this even relevant? After all, Einstein was just this guy, you know?

  • Duh! (Score:4, Funny)

    by UncleBiggims ( 526644 ) on Monday February 23, 2004 @10:20AM (#8361698)
    I doesn't take an Einstein... oh wait. Nevermind.

    Are you Corn Fed? [ebay.com]

  • No info... (Score:3, Funny)

    by eclectic4 ( 665330 ) on Monday February 23, 2004 @10:21AM (#8361706)
    ...in that article. I was hoping for a hint as to what dark energy is, but this article simply states possible changes in theory.

    At the end it states, "Understanding dark energy and determining the universe's ultimate fate will require further observations." Well great. Didn't we know this already? *sheesh!* Thanks for "almost" nothing....

    • Re:No info... (Score:2, Informative)

      by Silburn_Luke ( 672738 )
      If you want more detail you should check out the February issue [sciam.com] of Scientific American, which has four or five feature articles discussing the cosmological theories these experiments are addressing.

      Regards Luke

  • No, really? (Score:4, Funny)

    by TheGreatGraySkwid ( 553871 ) on Monday February 23, 2004 @10:24AM (#8361742) Homepage
    From the article:
    "Riess' team uses Hubble to find stars that exploded when the universe was about half its present age. A certain type of these supernovas, as they are called, shine with a known brightness."

    Supernovas, you say? Wow, what a fascinating new concept for readers of Space.com!

    I mean, come on!

  • Filling the blank? (Score:3, Funny)

    by cabazorro ( 601004 ) on Monday February 23, 2004 @10:28AM (#8361769) Journal
    I get the feeling that we are trying to fill
    a gap but with what???
    Observer: Look at those galaxies..they are moving appart.
    Braniac: Yes, that's because the big-bang long long time ago.
    Observer: They look very old and they appear to move slower as they drift compared to the young galaxies.
    Braniac: Of course, they are loosing momentum. But don't be deceived, at some point all universe is going to loose cohesion and become rippi-bits!
    Observer: Howbout that cluster over-there? Those galaxies are quite old and they are driftin faster than the young ones! What gives??
    Branica: Er ur..is dark energy pushing them appart, dark energy is spreading the galaxies.
    Observer: And the big bang.
    Braniac: yes, that too ..explosions and ever
    present dark-energy.
    Observer: Far out!
    Braniac:(scratching her head and punching madly
    at her calculator and giving a big sight of
    frustration)yeah, riveting.

  • http://www.ebtx.com/ntx/ntx16.htm (Score:5, Informative)

    by Anonymous Coward on Monday February 23, 2004 @10:46AM (#8361909)
    Whats more likely? This mysterous dark energy exists and compromises 70% of the mass/enery of the universe even though we can't see it anywhere locally, or our theories are wrong?

    I suggest reading www.ebtx.com on the nature of dark energy. This guy is right, or at least close.

    Matter attracts matter; this we know. The rest of the theory explains that space attracts space, and matter repels space. Matter and space are polar opposites (as well as logical opposites).

    Einstein wasn't relative enough in his theories. He declares C as constant and bases all other observations off it, when in fact you can change all the physical constants continuously and arrive at the same results. If C changed, as long as h, G, and about 18 other 'constants' also changed, we couldn't tell, from our point of view.

    Is the universe expanding, or are we all shrinking? From a relative point of view there is no difference.

    • Indeed... (Score:3, Funny)

      by master_p ( 608214 )
      C is the root of all evil!!!
    • Matter attracts matter; this we know. The rest of the theory explains that space attracts space, and matter repels space. Matter and space are polar opposites (as well as logical opposites).

      So is it then hypothesized that Space has similar parallels to matter? As certain kinds of matter can attract or repel other matter (electrons, protons), can one kind of space repel another kind of space? It would be interesting if "dark energy" was thought of as "anti-space".

  • Comment removed (Score:3, Informative)

    by account_deleted ( 4530225 ) on Monday February 23, 2004 @11:15AM (#8362148)
    Comment removed based on user account deletion
  • is how it's described in the article. I think that's a bit unfair. It can't help its appearance.

  • The main problem with Dark Energy... (Score:3, Informative)

    by little1973 ( 467075 ) on Monday February 23, 2004 @12:11PM (#8362609)
    ...is that no mainstream theory predicts its existance. It is based solely on observations. Scientists try to bend/modify current theories in order to include Dark Energy.

    Many formulas and theories are based on observations, however, a good theory not only describes current observations, but predicts things which are not observed, yet. Like Einstein's theory predicted time-dilation, the curvature of space-time, etc. and gave a solution to the orbit of Mercur (which Newton's theory was unable to explain).

    A new theory may be needed to include the Dark Enegy from its foundations or to explain these phenomenas without Dark Energy.

  • A "Circular" argument? (Score:2, Interesting)

    by Cragen ( 697038 )
    Whatever happened to the idea that something going away from us would eventually "re-appear" on the opposite side of the Universe and start heading towards us? (I have no clue what hypothesis was/is called.) Perhaps everything expanded to the edge, ALREADY, and is now "expanding" towards the center, again, and is therefore being more attracted to everything else cause it's getting CLOSER! (I have to stop now. My brain is going to take a little break.) Whew. Next?
    • Cragen (697038) sez: "Whatever happened to the idea that something going away from us would eventually "re-appear" on the opposite side of the Universe and start heading towards us?"

      It's still around, as an untestable hypothesis. It would take longer than the total lifetime of the universe to make the trip.

  • It's true that it's looking more and more like we live in a Universe with a nonzero cosmological constant. But that doesn't mean Einstein was right. Einstein introduced a nonzero cosmological constant for a very specific reason: to make a static universe. He lived at a time when the general metaphysical assumption was that the Universe was static and unchanging and had been around forever and always would be. So when he created his field equations and discovered that they insisted that, with a reasonab

  • w=-1

    This comes as a great shock to exactly no one. ;-) Postulating anything else is like introducing epicycles when you've only just figured out that there are orbits.

    [TMB]

  • Asimov (Score:2, Insightful)

    by gd2shoe ( 747932 )
    Isaac Asimov is certainly best known for his work as a science fiction writer. What most people don't know is that he also knew and enjoyed science. I don't have the understanding to discuss many of the theories that I have read here being debated, but I think something Isaac said once bears repeating. From his scientific work "The Neutrino", let me paraphrase:

    If you take a red ball, and throw it up in the air, you will observe it come back down. You can repeat the experiment with the same results. Yo

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