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Space Science

Einstein's Theory Improved? 456

Posted by ScuttleMonkey from the lots-of-rumblings-in-the-physics-world-lately dept.
skaet writes to tell us that A Chinese astronomer from the University of St Andrews claims to have fine-tuned Einstein's theory of gravity. Dr Hong Sheng Zhao has created a 'simple' theory which could "solve a dark mystery that has baffled astrophysicists for three-quarters of a century." This new law seeks to discover whether Einstein's theory was correct and if dark matter actually exists.
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Einstein's Theory Improved? More

Einstein's Theory Improved?

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  • Very interesting... (Score:5, Funny)

    by TheNoxx ( 412624 ) on Tuesday February 14, 2006 @05:38AM (#14714688) Homepage Journal
    Even if that is the worst graphic accompanying a well-written, intelligent article I've seen in my lifetime.

    • Re:Very interesting... (Score:2, Informative)

      by Anonymous Coward
      The article can be found at (pdf):
      http://www-astro.ulb.ac.be/Publications/bf_Zhao.pd f [ulb.ac.be]
    • Select "[Low Graphic Version]" at the top. Much better :)
    • Could be worse, could have wrote a paper entitled: "Using clipping planes to increase the graphical performance of showing 3d goatse men in real time"

    • Dark Matter is real, and here to stay (Score:4, Insightful)

      by Pausanias ( 681077 ) <pausaniasxNO@SPAMgmail.com> on Tuesday February 14, 2006 @01:59PM (#14717909)
      Dark Matter exists, and in my opinion it is here for good. The attempts to come up with alternative theories of gravity are quite noble, but they only work on certain scales, and the proponents of these theories sometimes neglect examples that invalidate their theory. It would be quite elegant to be able to account for dark matter via a modification of gravity alone, but I am afraid that it will not be possible.

      One of the most compelling pieces of evidence for the existence of dark matter is the "bullet cluster of galaxies" discovered by Maxim Markevitch and collaborators. Their 2004 peer reviewed article [harvard.edu] shows a small cluster of galaxies passing through much more massive one. As the cluster passes through, its gas is stripped, but the dark matter stays behind, detected via weak gravitational lensing. This effect is impossible to reproduce using alternative theories of gravity, because there is a visible separation between the total mass peak and the observable mass peak.

      There are dozens of other peer-reviewed articles that argue against these alternative theories of gravity. What about the cosmic microwave background [nasa.gov]? The CMB is one of the underpinnings of modern cosmology and basically made the big bang the widely accepted theory that it is today. This recent analysis of the CMB [harvard.edu] show that the kind of alternative gravity proposed here is strongly disfavored by the CMB spectrum, and that it would imply too high a neutrino mass [harvard.edu].

      I challenge you to look through the literature for yourself. Here is a list of papers [harvard.edu] discussing modified newtonian gravity and its derivatives... You will find that yes, these alternative theories do work quite well at describing the rotation curves of galaxies, as TFA suggest. But on larger scales, such as in cluster of galaxies and the cosmic microwave background, they seem to fail convincingly.
      • I see a few flaws in your well written and well linked post.

        First, and glaringly....you said:

        The attempts to come up with alternative theories of gravity are quite noble, but they only work on certain scales

        about scales, from TFA:

        A non-Newtonian gravity theory is now fully specified on all scales by a smooth continuous function.

        so, this yet to be reviewed theory claims to have overcome your first objection, and you cannot prove them wrong until April.

        you said:

        the proponents of these t

  • Law is for lawyers, not scientists (Score:4, Funny)

    by kooky45 ( 785515 ) on Tuesday February 14, 2006 @05:38AM (#14714689)
    Would people please stop using the word "Law" when referring to scientific theories. It confuses the creationists.
    • Name something that doesn't!
      • God's Law? ;-)

        Mind you, it confuses me... "Thou shalt not kill... Now go over that hill there and kill everyone you find"

        J.

    • Re:Law is for lawyers, not scientists (Score:5, Funny)

      by LordLucless ( 582312 ) on Tuesday February 14, 2006 @06:50AM (#14714857)
      Side-tracked into a religious flamewar withing 2 posts. That's got to be a first, even for slashdot.

    • Re:Law is for lawyers, not scientists (Score:5, Funny)

      by mikael ( 484 ) on Tuesday February 14, 2006 @07:16AM (#14714915)
      Cole's law - delicious!
    • Yeah, that's a joke, but it is also a pet peeve of mine

      "This new law seeks to discover whether Einstein's theory was correct..."

      Einstein's theory may be a theory, but this new "law" is only a hypothesis until it gains enough confirming experimental and observational evidence that most scientists in that field accept it as valid. Theories become law when they are basically irrefutable, e.g. 1st Law of Thermodynamics.

      • Re:Law is for lawyers, not scientists (Score:4, Informative)

        by Tim C ( 15259 ) on Tuesday February 14, 2006 @08:57AM (#14715421)
        Theories become law when they are basically irrefutable

        No, that's not what happens. Laws say what happens, theories say why and/or how it happens. Laws don't try to explain behaviour, they just state it. Hence the laws of thermodynamics are laws, while the theory of relativity is a theory and always will be.

        • and the "law" of gravity? (Score:5, Insightful)

          by FreeUser ( 11483 ) on Tuesday February 14, 2006 @10:15AM (#14715905)
          No, that's not what happens. Laws say what happens, theories say why and/or how it happens. Laws don't try to explain behaviour, they just state it. Hence the laws of thermodynamics are laws, while the theory of relativity is a theory and always will be.

          And the law of gravity? Observations say what happens. Theories say why and/or how it happense. Laws are what we call theories we think will never be falsified, and it's probably a word that should be dropped from any kind of scientific discussion, since we all should have learned by now that even the most basic assumptions and most obvious conclusions drawn from the most irrefutable of observations have a way of requiring revision from time to time, as better observations are made (Newton couldn't look at gravitational motion, and we cannot yet see into the higher folded dimensions of string theory, assuming such in fact exist).

          The "laws" of thermodynamics are as theoretical as relativity. Both have been observed, both are mathematically modelled to great precision, both make useful predictions, both are falsifiable, and no one outside of a few religious wackos expects either to be falsified. That doesn't mean they won't be.

          Someday we might find conditions in which entropy in a closed system decreases (candidates for something like this include the time leading up to the big bang--if such is found to have existed--and certain theories of the internal workings of black holes, etc.). Not that I or anyone else realistically expects this (but then, who expected the anomalies that would lead to the dark matter/energy vs. non-newtonian gravity debate, either), but the "laws" of thermodynamics are as falsifiable as the theory of relativity and, as it turns out, the "law" of gravity.

          Theories do have a habit of becoming "laws" when they are basically considered irrefutable. They shouldn't--we should probably refer to gravity as the theory of gravity, and the laws of thermodynamics as the theories of thermodynamics. It might stop the "big bang theory" and "theory of evolution" rhetorical nonsense we've all been subjected to by communications majors coasting through college with a "C" average only to become network anchors...and help all of us to think clearer. That having been said, I imagine my calls to refer to the laws of thermodynamics as the "theories of thermodynamics" would fall on my old physics professor's deaf ears. Most of us like keeping our language the way it is, no matter how cumbersome or confusing it becomes--but that's a rant for another day. :-)
          • I agree with the grandparent, and disagree with you.

            There's no governing body of scientific terms, but I've seen many proposed laws with no prior history of being called a theory. In my physics experience, laws are almost always a mathematical model of observed behavior with no attempt to explain the underlying reasons or mechanics of said behavior.

            Laws are theories as they fit all the definitions of a theory, but they don't become laws by extra proof, rather by their initial limited nature. For example,

  • Dark matter eh. (Score:5, Insightful)

    by squoozer ( 730327 ) on Tuesday February 14, 2006 @05:43AM (#14714704)

    I'm sure that there are lots of people that are far more clued up on this than I am that can find holes in what I am about to say but I always felt like dark matter was a bit of a fudge because we don't understand what is happening.

    My problem with dark matter is that it's almost as difficult to believe in as God. The only real proof we have is that the universe doesn't appear to move correctly without it. If that's as good as we can do then we might as well say God (or the FSM) is holding the universe together. To my mind it is a big leap from "the universe isn't moving as we expect" to "90% of the universe is made of something we can't see". Surely if the universe was full of this stuff we would be able to detect it because it would block radiation from distant galaxies - or is dark matter conveniently transparent?

    • Is dark matter conveniently transparent? (Score:5, Funny)

      by Savage-Rabbit ( 308260 ) on Tuesday February 14, 2006 @05:52AM (#14714733)
      My problem with dark matter is that it's almost as difficult to believe in as God. The only real proof we have is that the universe doesn't appear to move correctly without it..... or is dark matter conveniently transparent

      I have to disagree with that, I have no problem believing in the existance of dark matter. In fact I don't have to 'believe' in the existence of dark matter at all, I found some between my toes this morning and it was most certainly not transparent.

    • Re:Dark matter eh. (Score:5, Informative)

      by i_should_be_working ( 720372 ) on Tuesday February 14, 2006 @06:03AM (#14714758)
      Yes, most is actually transparent. There are many particles that don't interact with photons. They don't emit or absorb light, so therefore are impossible to detect with light and they can't block light either. A small percentage of dark matter is thought to be 'normal' matter that does reflect light, but the universe is big and not so bright. It's rare to get a chunk of rock or ball of gas reflecting much light in our direction. Astronomers have a hard time detecting planets many times larger than Jupiter

      For the reasons why dark matter must exist; some reasons are straight forward, some are more round-about-observations. The easiest one is from galaxies rotating too fast. The fact that they stay together means something is holding them together. Since we don't observe anything like a giant rope or hand of God holding our sun in place, the only logical explanation is gravity. Since we can't see enough matter to make this much gravity, it must be dark.

      The dark matter that's hypothesized because of the large scale curvature of the universe is not as straight forward, especially since it was recently found that the universe seems to be accelerating in it's expansion.

      I'd also like to point out that gravity, electrons and other particles or forces are no less valid than photons as observational tools. We really don't have to 'see' something to know it's there.
      • but the universe is big and not so bright.

        So we're all living inside a football player then? Damn, sure explains a lot...

      • Re:Dark matter eh. (Score:4, Insightful)

        by squoozer ( 730327 ) on Tuesday February 14, 2006 @07:17AM (#14714917)

        I certainly don't have a problem with the idea that we don't know everything. Perhaps my problem with dark matter is that it is reported in the press almost as if it is almost fact and yet in reality we haven't got any direct evidence. All we really have to go on is the fact that if dark matter didn't exist things, such as galaxies, wouldn't look like they do. If I had gone to my supervisor with an argument like that when I was doing chemistry he would probably have laughed himself stupid right before he sacked me. As for it not interacting with radiation thinking about it even if it did it could still be very hard to see. After all the universe is very big - you could easily hide something in it.

        In the spirit of good science hence forth I am going believe that the FSM holds galaxies together with his noodly appendages. The reason the speed with which the universe is expanding is increasing is easly solved by saving that the universe is created by the FSM using lazy initialization. We gain the ability to see further faster so the FSM has to push on the edge of the universe harder hence making the universe expand faster. Simple really.

        • Re:Dark matter eh. (Score:4)

          by DarenN ( 411219 ) on Tuesday February 14, 2006 @07:49AM (#14715045) Homepage
          Interestingly enough, Einstein himself believed strongly that dark matter existed, but (and this relates to your point) he could never prove it himself, so he left it out of the equation for fear of getting laughed at for such an unproveable notion.
          We must keep in mind that all the mathematical constructs we have at the moment are approximations. Newton's and Einstein's Laws are approximations that function well locally (in astronomical terms).

          It pays to keep an open mind on this subject (and all others) until it can be proved conclusively either way. Otherwise one is as bad as the church when it tried to suppress Galileo.
          • I think you confuse it with the cosmological constant (which today is linked to dark energy, which is something completely different than dark matter, except that we have even less of an idea what it actually is).
        • If I had gone to my supervisor with an argument like that when I was doing chemistry he would probably have laughed himself stupid right before he sacked me.
          So would I, if I was paying you to do chemistry but were faffing around with astronomy/astrophysics.

        • Re: Dark matter eh. (Score:4, Insightful)

          by Black Parrot ( 19622 ) on Tuesday February 14, 2006 @10:33AM (#14716063)
          > All we really have to go on is the fact that if dark matter didn't exist things, such as galaxies, wouldn't look like they do.

          We also have the fact that dark matter explains why things do look like they do.

          > If I had gone to my supervisor with an argument like that when I was doing chemistry he would probably have laughed himself stupid right before he sacked me.

          If you went to him with a (valid) argument that chemistry AWKI makes wrong predictions about some easy and repeatable observations, would he have sacked you?

          If you followed up with a hypothesis that explained all the anomalies with a single simple mechanism, would he have sacked you?

          > After all the universe is very big - you could easily hide something in it.

          Yes, but that something would have to be in the right place to explain the gravitational anomalies, and given our observations of that place, it would have to be "hidden" in a certain kind of way.

      • Re:Dark matter eh. (Score:3, Insightful)

        by hswerdfe ( 569925 )
        the only logical explanation is gravity

        point of fact, I think you mean one of the following :
          * the only logical explanation I can think of is gravity.
          * A logical explanation apears to be gravity.

        normally I wouldn't complain being /. and all
        but still, science needs to be respected for what it is, and not what some would have it be

    • Re:Dark matter eh. (Score:2, Insightful)

      by Daengbo ( 523424 )
      I initially found it amusing when dark matter began to be discussed seriously, because originally, there was the "Ether" (a substance which we can't see or measure in space), then it was laughed at as absurd, then something stikingly similar appeared in the form of dark matter. Why don't we just rename dark matter to ether and be done with it?
      • My father used to believe in Ether as long as he lived.
        He used to explain to us when we were kids, about ether filling up the space between sun and earth. Am talking about 1983-84...

        Methinks, dark matter is either subspace, OR, gravitational constant varies wildly between various regions in space, thus altering the fundamental constant.
        We may live in a bubble which has 9.8 m/s as gravity on earth. Voyager, which is out of solar system may have entered another such region where it varies....

      • Re:Dark matter eh. (Score:3, Informative)

        by Phleg ( 523632 )
        Because aether is a fundamentally different concept from dark matter. aether was presumed to be the fabric of space itself--a massless medium for the purpose of transmitting forces across "empty" space. On the other hand, dark matter is simply theorized as matter which doesn't interact with photons.
    • Yes, Dark Matter is invisible and undetectable in every way except by its uncanny ability to make our equations wrong. It's impossible that our equations don't really apply to galaxies. Although, the fact that they don't apply to super small particles should have been a clue that they aren't perfect.

      I personally, have a complete dislike for the idea of dark matter. It seems like a stab in the dark, that missed, and was declared right anyway. "Wow, galaxies spin way faster than we think they should. It's alm

      • Re:Dark matter eh. (Score:3, Interesting)

        by wanerious ( 712877 )
        I personally, have a complete dislike for the idea of dark matter. It seems like a stab in the dark, that missed, and was declared right anyway. "Wow, galaxies spin way faster than we think they should. It's almost like there are invisible halos of super heavy matter surrounding all galaxies." Oh, yeah, beyond being completely invisible Dark Matter exists in halos around galaxies. They are really really heavy but the stars don't fall into the halos or the halos into the stars. It's all magically perfect.
    • I also don't like dark matter/energy theories very much (although I do like the idea that there is more out there that we don't know about). Nor do I like string theories. I think the whole of physics is somehow run amok. A few things do appeal to me however, probably because of my feeling that ultimately it all boils down to a computational algorithm. I think that some aspects of quantum theory fit like the "Bekenstein bound", and that this relates to gravity over the large scale.

      For example, when it c
    • > My problem with dark matter is that it's almost as difficult to believe in as God. The only real proof we have is that the universe doesn't appear to move correctly without it.

      Ah, but the universe doesn't behave correctly in three distinct ways - galaxy rotations, binding of galaxy clusters, and gravitational lensing - and all three are elegantly explained by the simple hypothesis that the visible matter in the cosmos is embedded in halos of "invisible" matter.

      Moreover, the current state of particle ph
  • How exactly would the law itself discover anything? Wouldn't that have to be a hypothesis first that would have to be tested experimentally before it becomes a law?
    • As other people have pointed out, the word 'law' is not used (anymore) in science; if a hypothesis is experimentally verified, its status becomes a 'theory'. The word 'law' would indicate that it's results are set in stone; this is never the case in science.

  • Article should present his theory (Score:3, Insightful)

    by MichaelSmith ( 789609 ) on Tuesday February 14, 2006 @05:45AM (#14714715) Homepage Journal
    The new formula will be presented to an international workshop at Edinburgh's Royal Observatory in April

    Won't it be ready until April? Stranger things have happened.

  • Restorative (Score:5, Insightful)

    by FishandChips ( 695645 ) on Tuesday February 14, 2006 @05:47AM (#14714721) Journal
    What a clear and well-written article. And what a pleasant, unassuming statement from Dr Zhao:

    "A non-Newtonian gravity theory is now fully specified on all scales by a smooth continuous function. It is ready for fellow scientists to falsify. It is time to keep an open mind for new fields predicted in our formula while we continue our search for Dark Matter particles."

    Even if the theory turns out not to stand up, words like this take us back to what makes science interesting and important. That "falsify" is worlds away from the publicity hounds and egomaniacs who so often represent science to the lay reader.

    • Re:Restorative (Score:4, Interesting)

      by lightversusdark ( 922292 ) on Tuesday February 14, 2006 @06:24AM (#14714798) Journal
      I second that sentiment, and presume that he means it - with the publication of not just his office number, but his personal mobile (cell) number as well!
    • ..and further proof that scientists are not dogmatic but actually explore the evidence and make hypotheses: the most convincing evidence I've seen for the existence of dark matter (rather than MOND) is from HongSheng himself in comparing the two body relaxation time of globular clusters compared to dwarf galaxies of the same mass (see astro-ph/0511713 [arxiv.org]).

      [TMB]

  • Model! (Score:2, Insightful)

    by diquark ( 833853 )
    Although it is not the theory that has been improved, it is the model. It takes a simple function to interpolate between the dark matter area (which is non Newtonian - Modified Newtonian Dynamics or MOND) and the Newtonian area, where baryonic matter seems to reign. Despite a simple continuation function for the two areas, the authors find a nice agreement with rotation curves of galaxies including our own, and some external ones. The theory which has been used is the TeVeS (Tensor Vector Scalar) theory by

  • Completely irrelevant - St Andrews (Score:5, Informative)

    by Flying pig ( 925874 ) on Tuesday February 14, 2006 @06:25AM (#14714802)
    For those who may not know, St. Andrews is an ancient Scottish university which has a long involvement with astrophysics. When I considered going there, all those years ago, students still wore gowns in public - I wonder if they still do.

    Unfortunately, like Cambridge, St. Andrews has suffered from negative publicity as a result of its taking occasional pupils from failing schools and admitting them with A level scores which would not normally allow a student to be admitted. But at least it meant that some of the Windsors got access to higher education, so perhaps the policy is defensible.

    Anyway, I'm very pleased that the astrophysics tradition is continuing. But I'm still left with a question: Why are the nicest British Universities (Cambridge, Durham, St Andrews) in such bloody cold places?

    • Re:Completely irrelevant - St Andrews (Score:5, Interesting)

      by david.given ( 6740 ) <dg@cowlark.com> on Tuesday February 14, 2006 @06:50AM (#14714858) Homepage Journal
      For those who may not know, St. Andrews is an ancient Scottish university which has a long involvement with astrophysics. When I considered going there, all those years ago, students still wore gowns in public - I wonder if they still do.

      I did go there --- it's a great place (and the bright red gowns are no longer compulsory, although you get free entry to the castle if you wear your gown). I did first year astronomy before realising that my maths weren't up to it and switching to comp sci; St. Andrews has some genuinely decent telescopes [st-and.ac.uk] despite being at sea-level in a built up area. The Greg is deeply impressive to go and see. It's amazing just how big it is.

      For those who don't know, St.Andrews is the third oldest university in the UK, after Oxford and Cambridge; it was founded in 1413, and totally dominates the town. (The university owns most of the town centre.) Going there is an experience totally unlike any other university in Britain... I had a room in a hall of residence five minutes walk from the town centre, perched high on a cliff top overlooking the North Sea. Great view.

      Unfortunately, like Cambridge, St. Andrews has suffered from negative publicity as a result of its taking occasional pupils from failing schools and admitting them with A level scores which would not normally allow a student to be admitted. But at least it meant that some of the Windsors got access to higher education, so perhaps the policy is defensible.

      Actually, things have changed. Until very recently, British students got their tuition fees paid by the state. Not long ago, however, the British parliament voted to make them pay a proportion --- but the Scottish parliament didn't. So students who go to a Scottish university get their tuition fees paid for them. As a result, all the Scottish universities have been inundated with students, and as the highest-prestige university in the country, St.Andrews can now basically name their price.

      That doesn't explain Prince William, however, who is by all accounts not very bright.

    • Why are the nicest British Universities (Cambridge, Durham, St Andrews) in such bloody cold places?

      Nice, you've basically spanned near enough the entire UK with that statement. Whilst Edinburgh is in the far north of the UK (Scotland) and Durham in n the far north of England, Cambridge can only be described as being in the south (unless of course you're a cockney zealot who claims everything north of the river is north). And, the best thing is that the statement is still correct - everywhere in the UK

  • Dark matter, I don't buy it (Score:3, Interesting)

    by Opportunist ( 166417 ) on Tuesday February 14, 2006 @06:36AM (#14714824)
    I am not an astronomer. I just tend to apply logic to everything I collide with.

    And when I can't collide or interact with it, it kinda ruffles me the wrong way. What kinda magical stuff is this supposed to be. Doesn't interact, doesn't shine, doesn't emit, doesn't absorb, all it does is offer some convenient gravity to explain a few things that don't make sense otherwise.

    It kinda reminds me how about 500 years ago astronomers came up with double and triple rotations of planets around an imaginary point to explain why the planets move the way they move since they believed the Earth and not the sun is the center of our system. And if they rotated around earth, they had to jump through a few hoops to explain that odd orbits they showed. Instead of abandoning the system that didn't work and accept one that does, they religiously clinged to it and tried to explain what could not be explained.

    Maybe we're at that point again?

    Maybe, just maybe, it's not dark matter but some of our "laws" are simply wrong. Or, if not wrong, they maybe don't extrapolate well into the larger scale, what works and makes sense in the (comparably) small scale of our solar system doesn't make sense and doesn't work on a galactic scale.

    I do hope this is a step into the right direction. Science is all about not setting stuff in stone. Everything has to be questioned, everything has to be tested, even the most holy scriptures from the most revered astronomers of all times should be ripped if they showed an error.

    If not, science is no better than religion.

    • Your history isn't quite right (Score:4, Insightful)

      by Flying pig ( 925874 ) on Tuesday February 14, 2006 @07:05AM (#14714887)
      In fact, from the point of view of generating a mathematical model of planetary orbits from observation it doesn't matter whether the Earth or the Sun is taken as the centre (especially since neither is correct.) The problem was not ad hoc explanations - it was that Aristotle had said that heavenly bodies moved in circles, the Church had bought into this, and in dealing with the Church (just like today with biology) scientists had to be careful. So in order to explain actual motions they used combinations of circles called epicycles. Nikolaus Kupfernigk claimed, over 500 years ago, that the epicycle model was simplified if the Sun was at the centre - but, as he was working to better observations that existed in the past, he actually needed more epicycles than earlier astronomers. It was not surprising that there was dispute over his findings.

      It was Kepler who realised that ellipses could be the correct model for orbits, and even there, to try and keep the Church happy, he tried to fit the major and minor axes into the shapes of the "Platonic solids".

      History suggests that the example you are quoting is the opposite of what you want to show. It is better to let scientists come up with initially ad hoc explanations because they lead to the truth. Making initial unscientific assumptions and treating them as dogma suppresses and delays progress. Scientists are ambitious and a good way to become important is to replace someone else's theory - so scientists can be relied on to do that. For every established Dark Matter theorist there are probably several PhD students who would love to annihilate Dark Matter.

      The line of argument in the parent annoys me because it tries to suggest that scientists left to themselves will produce ridiculous non-explanatory theories and then cling to them forever. It's the anti-scientific agenda of the Creationists who want to discredit science. Creationists and their like want to confuse the public as to the explanatory status of different scientific theories so they can claim their snake oil is on an explanatory par with plate tectonics, quantum electrodynamics or evolutionary biology.

    • Well, logically, when you figure out that stars don't orbit galactic centers as you expect you can theorize that gravity is not acting as you expect, or you can theorize that gravity is acting as expected, and that there is mass that you cannot detect through other means.

      If you a nineteenth century astronomer and you noticed that Newtonian physics didn't accurately predict the orbit of Mercury, would you come up with the theory of relativity, or would you look for Vulcan [wikipedia.org]? I agree with you that Dark Matter

      • I agree with you that Dark Matter seems to be the 21st-century equivalent of searching for Vulcan, but trying to explain the observation without changing the theory of gravity was not necessarily a stupid thing to do, and it's a heck of a lot more straightforward than developing a new theory.

        Note that the "Vulcan strategy" was already successful in the case of Neptune. So here we have one case where the additional-matter theory turned out right (Neptune), and another where it turned out wrong (Vulcan).

    • Maybe, just maybe, it's not dark matter but some of our "laws" are simply wrong.

      Of course our theories are wrong. No scientist believes he has the discovered the absolute truth. But our theories are as good as they can be, given the current evidence.

      In the case of dark matter, you have a single unknown blip in an otherwise elegant series of equations that explain a huge proportion of the data that astronomers can observe. Scientists knows that within this blip lies a messy tangle that will eventually d
    • And when I can't collide or interact with it, it kinda ruffles me the wrong way. What kinda magical stuff is this supposed to be. Doesn't interact, doesn't shine, doesn't emit, doesn't absorb, all it does is offer some convenient gravity to explain a few things that don't make sense otherwise.

      So does glass, but you aren't talking about how glass is magical are you? I'm haven't really formed a solid opinion on this dark matter thing but I'm certainly of the idea that it's most definitely possible. Is it
      • I didn't mean to say that Dark Matter has to be wrong just because it cannot be proved (yet). All I wanted to say is that we should maybe not cling to it too tightly and consider that it might be wrong, and that there should be room for other theories that explain this phenomenon.

        It is probably currently the best theory we have (and, granted, I don't have a better one in my pocket). That doesn't mean it's the only reason why objects in space behave so "strangely" as they do. Somebody already mentioned Vulca
    • On what exactly are you basing your sentiment that science should be better than religion? Better for what?

      The statement that "science is/isn't better than religion" is not scientific, it's rather religious.

    • Neutrinos (Score:4, Insightful)

      by Detritus ( 11846 ) on Tuesday February 14, 2006 @08:38AM (#14715297) Homepage
      Although I share your skepticism about dark matter, I couldn't help thinking about the neutrino, a "hidden" particle that filled another gap in physics. It took 25 years for physicists to finally detect the neutrino.
  • The link at the bottom of the page labelled "About PPARC [pparc.ac.uk]" obviously goes too close to a singularity and ends up in a parallel universe with a quantum difference of this address is a 404 page. They've got me convinced.

  • I want his job! (Score:4, Funny)

    by Ancient_Hacker ( 751168 ) on Tuesday February 14, 2006 @07:24AM (#14714943)
    There are two kinds of jobs in the world:

    (1) Jobs where if you goof up, some money goes down the drain, or you're embarrassed or, somebody gets hurt or dies. You know, like being a doctor or lawyer or engineer.

    (2) Jobs where it doesnt matter one whit if you're wrong. Jobs like theoretical physicist in a field where there isnt the slightest possibility of carrying out an experiment. Such as dabbling in the theory of gravity.

    Like an idiot, I'm in category #1. What a dope.

  • E = mc^2 and sometimes Y.
  • ... just last week or so, we were told there was *no question* that it exits; we're just studying it's properties now. No question *at all*: commence ridicule of any who disagree.

    Just who are we supposed to ridicule now? Would someone please give me my nerd marching orders?
    • Here you go ...

      01001000 01100101 01110010 01100101 00100000 01100001 01110010 01100101 00100000 01111001 01101111 01110101 00100000 01101110 01100101 01110010 01100100 00100000 01101101 01100001 01110010 01100011 01101000 01101001 01101110 01100111 00100000 01101111 01110010 01100100 01100101 01110010 01110011 00101110 00100000 00100000 01001100 01100101 01100001 01110110 01100101 00100000 01001110 01101111 01110111 00100001
  • Or am I the only one who is almost completely jaded to "Yet another theory this year that challenges our understanding of the universe".
    Our we all jehovahs Whitnesses or what?
    Oh wait, I guess every project needs funding. More importantly every scientist needs funding and since global warming is taboo via near Presidential verdict, lets go after dark matter and the E-man himself.
    Almost easier if you go after Darwin, oh except thats not physics and that is also taboo due to political unrest given this semi-ne
  • PPARC still posts the scientists e-mail addresses in tfa? I can think of many spam e-mails that contain 'dark matter' but not of the kind they're looking for!

  • Here is the arxiv preprint (Score:4, Informative)

    by Anonymous Coward on Tuesday February 14, 2006 @08:11AM (#14715153)
    http://arxiv.org/abs/astro-ph/0512425 [arxiv.org] The phenomena customly called Dark Matter or Modified Newtonian Dynamics (MOND) have been argued by Bekenstein (2004) to be the consequences of a covariant scalar field, controlled by a free function (related to the MOND interpolating function) in its Lagrangian density. In the context of this relativistic MOND theory (TeVeS), we examine critically the interpolating function in the transition zone between weak and strong gravity. Bekenstein's toy model produces too gradually varying functions and fits rotation curves less well than the standard MOND interpolating function. However, the latter varies too sharply and implies an implausible external field effect (EFE). These constraints on opposite sides have not yet excluded TeVeS, but made the zone of acceptable interpolating functions narrower. An acceptable "toy" Lagrangian density function with simple analytical properties is singled out for future studies of TeVeS in galaxies. We also suggest how to extend the model to solar system dynamics and cosmology, and compare with strong lensing data (see also astro-ph/0509590).
  • They have created a formula that allows gravity to change continuously over various distance scales and, most importantly, fits the data for observations of galaxies...It is time to keep an open mind...

    There is not much in this article that gives us a clue as to what they are referring to. But I guess we have to wait for their Edinburgh presentation in April.
  • "The new formula will be presented to an international workshop at Edinburgh's Royal Observatory in April, which will be given the opportunity to test and debate the reworked theory. Dr Zhao and Dr Famaey will demonstrate their new formula to an audience of Dark Matter and gravity experts from ten different countries."

    No preassure. *phew*

  • My intuition says this is not going to hold up. Firstly, this seems to be an ad hoc theory to explain the fact that galaxies rotate too quickly. There's nothing wrong in ad hoc theories as such, but when it comes to theories like Newton's and Einstein's theories for gravity, they are so well tested that I would expect any amendment to be based on something more substantial.

    Secondly, Newton's formula for gravity around a point mass (on which Einstein's theory is based) seems to fit very well with one's intui

  • My opinion as a physicist (Score:5, Informative)

    by Anonymous Coward on Tuesday February 14, 2006 @09:51AM (#14715757)
    First off, I want to say a few words about dark matter. I think it's kind of irritating when people rant on about how dark matter is ad hoc fudging, etc. etc. Well, "fiddling around with the laws of gravity" isn't any better on that account. The fact of the matter is that all of theoretical physics is creating new models that fit our observations, and both dark matter and MOND fall into that category. The very existence of MOND as a theory shows that it is not easy to distinguish "matter that primarily interacts gravitationally" from "modifications to the laws of gravity". Historically, both "unseen matter" and "modifications to gravity" have been valid solutions to anomalous gravitational behavior (in the cases of Neptune's orbit and the perihelion precession of Mercury, respectively).

    As it stands, dark matter models can pass many experimental tests, and they're still the way to bet. That being said, MOND is not a bad idea either. It's not as well supported by dark matter, and it has serious problems with galaxy clusters, but it can still account for a surprising amount of data [uchicago.edu] (for a nonrelativistic theory!). The flaw of non-relativistic has been "corrected" by Bekenstein's TeVeS theory [arxiv.org] (the one that Zhao and Famaey's work [arxiv.org] is based on).

    Unfortunately, TeVeS appears to be rather ad hoc [google.com] (even compared to dark matter). Z&F's work does not appear to be much better in this regard. In addition, solar system observations appear to place serious constraints [arxiv.org] on such MOND-like theories, leading to anomalous non-inverse square forces in the outer solar system (and no, it doesn't seem to be of a form that can be attributed to the Pioneer anomaly [arxiv.org], though the jury is still out).

    The TeVeS/dark matter debate should be definitively resolved by the Planck mission [esa.int], which will be capable of resolving the third acoustic peak in the the cosmic microwave background radiation power spectrum. TeVeS and dark matter make very different predictions [uchicago.edu] for the structure of this peak. Of course, if TeVeS fails this test, maybe some other MOND-like theory could be put forward (if the entire class of theories hasn't already been ruled out by other means, such as solar system dynamics, by then).

  • MOND in the Solar System (Score:3, Informative)

    by Betelgeuse ( 35904 ) on Tuesday February 14, 2006 @10:30AM (#14716042) Homepage
    For those that are interested in this, Jacob Bekenstein (the author of the first relativistic MOND paper ~2 years ago) has a paper [lanl.gov] on the preprint server today about the possible measurable effects of MOND in the solar system.

  • Seductive elegance (Score:5, Interesting)

    by tm2b ( 42473 ) on Tuesday February 14, 2006 @10:52AM (#14716221) Journal
    They say that nature abhors a vacuum. When I was working to finish my Physics degree, we had a saying:
    Physicists abhor a 2nd order differential equation.
    The more elegant (usually meaning simple) a theory is, the more we feel that we've arrived at a "deeper" understanding of the universe. And that's what drives most physcists.

    The problem is that as a result physicists really, really like very elegant theories when there's no particular reason to believe that the Universe itself has the same bias. Similarly, we like to take theories that work on scales and locations that we know and can easily interact with, and assume that they smoothly apply in the places that we can't get to know quite so easily. It's reasonable even if it isn't logical - we have to go with what we already have. It's a decision born of practicality.

    In Cosmology, there's even a phrase for this: we assume homogeneity and isotropy. That is, that there's nothing special about where and when we are, and that the universe is pretty much the same (in physical laws) everywhere. The first time I heard about "dark matter," it was in the context of closure of the Universe. Physicsts really really wanted the universe to have enough mass/energy in order to be "closed," but we simply weren't finding enough matter. There was no reason to believe that the universe is closed (curvature 1.0), but it just seemed more elegant. So, they started to look for the "missing mass."

    These are not logical assumptions, they're just assumptions that we have to make in order to get anywhere. Again, there's no reason that the universe will cooperate on this matter.

    My own bias is to reject dark matter in favor of a revised theory of gravity, but that's just my own love of elegance - a different gravity feels more elegant than dark matter and dark energy, and in fact would hint at much more interesting cosmologies. But that's just how I am seduced by elegance...

    • Re:Seductive elegance (Score:3, Insightful)

      by phliar ( 87116 )

      The problem is that as a result physicists really, really like very elegant theories when there's no particular reason to believe that the Universe itself has the same bias.

      Start by reading Wigner's The Unreasonable Effectiveness of Mathematics in the Natural Sciences [dartmouth.edu] (also available at many other web sites.)

      We may not have any reason to believe that the Universe is elegant, but we also have no reason to believe that it isn't. So when we find that two very simple and elegant theories (QM and GR) des

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