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MOST of the small satellite galaxies around the Andromeda galaxy are lined up in a single plane that slices through its spiral disc, an alignment that suggests the satellites are floating on a river of dark matter.

Seeing regularities in the midst of a huge number of other possibilities is, really, suggestive of something other than chance. Seems like scientists do it all the time. In fact, it appears easy to do. Keep reading.

Using the Hubble Space Telescope, Eva Grebel of the University of Basel in Binningen, Switzerland, and her colleagues found that nine of Andromeda’s 14 satellite galaxies lie in a relatively thin plane about 52,000 light years wide.

“It’s unlikely such a plane would arise by chance,” Grebel says, who presented the results at a meeting of the American Astronomical Society in Washington DC. The satellites in the plane also have similar characteristics – most are faint, low in mass, and no longer form stars.

According to Grebel, one of the more intriguing explanations for this observation is that the galaxies may have fallen towards Andromeda along an invisible filament of dark matter. Computer simulations have shown that such filaments can form a cosmic “web” along which galaxies flow, and maps of the universe’s large-scale structure reveal thousands of galaxies lining up along intersecting streams. “One question is, could we see such filaments in our immediate surroundings?” says Grebel.

Two other articles on the subject of dark matter, gravity, relativity, etc:



Gravity theory dispenses with dark matter

New Scientist 11:01 25 January 2006

A modified theory of gravity that incorporates quantum effects can explain a trio of puzzling astronomical observations – including the wayward motion of the Pioneer spacecraft in our solar system, new studies claim.

The work appears to rule out the need to invoke dark matter or another alternative gravity theory called MOND (Modified Newtonian Dynamics). But other experts caution it has yet to pass the most crucial test – how to account for the afterglow of the big bang.

Astronomers realised in the 1970s that the gravity of visible matter alone was not enough to prevent the fast-moving stars and gas in spiral galaxies from flying out into space. They attributed the extra pull to a mysterious substance called dark matter, which is now thought to outweigh normal matter in the universe by 6 to 1.

But researchers still do not know what dark matter actually is, and some have come up with new theories of gravity to explain the galaxy observations. MOND, for example, holds that there are two forms of gravity.

Above a certain acceleration, called a0, objects move according to the conventional form of gravity, whose effects weaken as two bodies move further apart in proportion to the square of distance. But below a0, objects are controlled by another type of gravity that fades more slowly, decreasing linearly with distance.

But critics point out that MOND cannot explain the observed masses of clusters of galaxies without invoking dark matter, in the form of almost massless, known particles called neutrinos.
Quantum fluctuations

Now, Joel Brownstein and John Moffat, researchers at the Perimeter Institute for Theoretical Physics and the University of Waterloo in Ontario, Canada, say another modified gravity theory can account for both galaxies and galaxy clusters.

The theory, called scalar-tensor-vector gravity (STVG), adds quantum effects to Einstein’s theory of general relativity. As in other branches of physics, the theory says that quantum fluctuations can affect the force felt between interacting objects.

In this case, a hypothetical particle called a graviton – which mediates gravity – appears in large numbers out of the vacuum of space in regions crowded with massive objects such as stars. “It’s as if gravity is stronger” near the centres of galaxies, Brownstein told New Scientist. “Then, at a certain distance, the stars become sparse, and the gravitons don’t contribute that much.” So at larger distances, gravity returns to the behaviour described by Newton.
Pioneer 10 anomaly

Brownstein and Moffat tested the theory in several ways. They estimated that their gravitational change occurs 46,000 light years out from the centre of a large galaxy and half that distance for a small galaxy. They applied these estimates to 101 observed galaxies, and found that both their theory and MOND could account for their rotations. “The point is that neither of the two theories had any dark matter in them,” says Brownstein.

But the theories did diverge when the pair tested them against observations of 106 galaxy clusters. MOND could not reproduce the observed cluster masses but STVG accounted for more than half.

Furthermore, the team tested the theory against observations of NASA’s 34-year-old Pioneer 10 spacecraft, which appears about 400,000 kilometres away from its expected location in the outer solar system. Brownstein says the theory fits observations of the so-called Pioneer anomaly (see New Scientist feature, 13 things that do not make sense), while MOND cannot address it because Pioneer’s acceleration is above a0.
Big bang’s afterglow

“At three different distance scales, we see answers that agree with experiment,” says Brownstein. “They are claiming they can solve all the world’s problems,” agrees Sean Carroll, a cosmologist at the University of Chicago in Illinois, US. But these experiments are “not what most cosmologists would first think of if they were going to test a new theory of gravity”.

He says any theory must also explain the development of large-scale structures in the universe, and most importantly, the afterglow of the big bang. Called the cosmic microwave background (CMB) radiation, this afterglow was produced about 370,000 years after the big bang when the first atoms formed and has been studied in great detail by satellites, such as NASA’s WMAP probe.

“The dark matter model is not perfect, but it made a very specific prediction for the microwave background that seems to be coming true, and it fits galaxies and clusters and large-scale structure and gravitational lensing,” Carroll told New Scientist. “Nobody would be happier than me if it turned out to be modified gravity rather than dark matter, but it’s becoming harder and harder to go along with that possibility.”

Brownstein says the team is currently testing its theories with work on CMB studies.

Sorry about editing your post, PaV, but I figured it was better than creating an entirely new one and dividing the conversation.


well, talking about physics is a tricky subject---people often mean different things by the same words. I think there is a meaningful sense in which there is, *by definition* only one universe. glad the earlier comments helped, anyway. all the best physicist
physicist "i’d need you to define clearly what you mean by universes, and then you’d need to be prepared for me to be unsure about the answer! at the moment your question isn’t well-posed enough for me to respond—often the question of number of universes is just semantic" That told me all I needed to know. Thanks. DaveScot
sorry---that is a bit harsh. anyway, dark matter and dark energy are both interesting proposals and worth reading more about. not sure if it is relevant to ID, though. all the best physicist
PaV “It’s sort of like an ‘Unmoved Mover’: we don’t see it; can’t detect; don’t know its nature; yet we can detect its effects in our world.” PaV, I still object to some your characterization, here. `Seeing' is irrelevant for particles that don't interact with photons---there is no reason to expect that all particles interact with light. True, we don't know as much as we'd like about its nature, and certainly less than a lot of other matter. But again, I'd point out that saying we `can't detect' it contradicts `we can detect its effects in our world'. I don't think it's any more like an `unmoved mover' than any other area of physics we'd like to investigate further. Perhaps you can justify the statement more but I don't think you have, yet. I don't know if you are very familiar with theoretical physics in general, but let me warn that it is foolhardy to rely on intuition if you are not. (Sorry if that sounds harsh!). physicist
physicist: You wrote: "PaV, i’d be interested in your response to #4—I think you’re being quite hasty in dismissing dark matter." In my remarks, I was not trying to dismiss dark matter. In fact, I was trying to show the similarity between an indisputable "scientific" argument being made in the absence of a detailed, replete knowledge of a particular phenomena--just as with an 'intelligent designer'; e.g., who is it? what kind of a designer is it? etc., etc.--and the kinds of intellectual inferences we are still allowed to make--scientifically!--regarding the phenomena that we can observe, can describe in detail, that are seen as an 'effect' of an, as yet, unknown 'cause'. My sense of the Dark Energy/Dark Matter problem is that we might possibly be looking at another, as yet unknown, force. Just an intuition; but certainly I don't dismiss either notion of DM or DE. PaV
none taken---and i'd still be interested to know what he thinks of what i've tried to explain about the physics involved in #29 and #30. it's an interesting subject, and i agree with dave that juries are still out. it's just the problems can't be convincingly solved by making unjustified assertions.... physicist
physicist, Dave can be "abrupt". It's his personality. Try not to take offense. Bombadill
PS i'm very surprised you think I'm in a `lala-land of theoretical nonsense', and i doubt this is a description other people reading this thread or blog would recognise! what did i say that made you think this? physicist
davescot I don't think you need me to answer the question to read and understand what i've written above, but... ...for me to respond, i'd need you to define clearly what you mean by universes, and then you'd need to be prepared for me to be unsure about the answer! at the moment your question isn't well-posed enough for me to respond---often the question of number of universes is just semantic. i'd hope that my comments above and elsewhere on the blog will be good evidence that i am grounded in reality. i'm also fairly well-grounded in physics, and would be happy to explain more if you ask me specific questions. physicist
physicist I want to hear your anwer on how many universes you think there are in order to decide if you're well enough grounded in reality for me to want to have any further discourse with you. DaveScot
Davescot I'm really not sure you've understood what I mean in #29 and #30. I'm not talking about multiple universes, I'm just talking about classical physics and astronomical observations of supernovae, and warning that including quantum effects in a gravitational theory is very tricky. if you would like me to explain more about this, I'd be happy to. physicist
physicist To be perfectly honest the salient question is whether you understand them. I'm quite convinced at this point you're out in some lala-land of theoretical nonsense. How many universes are there? DaveScot
I edited the original post to include some links related to the conversation. Patrick
Davescot I think you're conflating a number of ideas in theoretical physics here---do you understand what I mean in my comments #29 and #30? physicist
I better duck out of this one now. As Bill O'Reilly would say "I'll let you have the last word, sir." DaveScot
The last space shuttle to crash was almost perfectly designed. All we needed was 3 extra grams of foam in just the right spot and it would have been perfect. No need to get all concerned about reevaluating our design parameters - a dab of hot glue should do the trick! What's wrong with that picture? LOL! DaveScot
This mindset of salvaging pet theories with ad hoc kludges to explain failed predictions is what propped Darwin up for so long. I see it's not just biology that is plagued by this. Us engineers are a different breed I guess. Lives can be lost when we're wrong so we can't afford to let our egos get in the way of acknowledging failures. DaveScot
David H I didn't know science had become the art of salvaging theories with failed predictions by the addition of ad hoc hypotheses like smidgins of constants to equations that hadn't needed them for the past 75 years. Excuse me. GR is in fine shape. It just needed a little work is all. The jury I guess has come in. I'm curious, is there anyone on the jury in addition to David Heddle? DaveScot
so i would just re-emphasise that at the classical level, if you want to explain cosmological observations of type Ia supernovae, making lambda non-zero is indeed the simplest modification to GR you can make---and fits the observations well. physicist
Davescot At the level of classical GR there is no preference for a particular value of Lambda one can only go so far with QFT on curved backgrounds---I agree the naive value of Lambda predicted is incorrect, but there is a lot more to the story of quantum effects and gravity. including quantum effects in gravity is a general a very hard and unsolved issue. so i wouldn't say the QFT indication of a large Lambda is a firm `prediction'. it has always been recognised that combining QFT and GR in this way is an ambiguous procedure. so i think kludge is misapplied. if you want to look for fine tunings, there are lots of other constants in nature which are finely tuned--for example the precise mass ratios of fundamental particles. if you want to explain these numbers by design, you can---but part of the study of physics is seeking to find deeper and simpler underlying reasons for these apparently finely tuned numbers. physicist
physicist re CC += GR (how's that for cryptic?) :-) The only problem with calling that the most conservative thing to do is that the amount of CC you're adding is 120 orders of magnitude smaller than most QFT's predict. And therein lies Heddle's point about support for cosmological ID. The infinitesimally small value is like the mother of all fine tunings. In engineering when things don't work out quite like we predict and we do something like this to fix our model it's called a kludge and it isn't a complimentary term. Do you use that term in physics? If not you should. DaveScot
Dave Scott, Regardless of what he meant regarding the galaxy, there is no ToR breakdown. That is simply wrong. A non-zero CC does not violate GR, it’s a term that, after realizing the universe was expanding, Einstein decided he didn’t need, since he wanted to use it to explain a steady state universe. My guess is, since it now seems to be needed, he’d be delighted at its rehabilitation. Also, you imply that the CC was pulled out of the air to explain accelerated expansion. In fact, it has been recognized for sometime, prior to the recent observations, that a vacuum energy density looks like a cosmological constant—it was already making a comeback. Furthermore, the CC contributes to the understanding of not just the accelerated expansion, but also the other big cosmological news: the flatness of the universe. (And also the "age" problem) Yes the jury is still out. It often stays out for a long time in science. David Heddle
PaV, i'd be interested in your response to #4---I think you're being quite hasty in dismissing dark matter. physicist
sorry that last comment to david heddle physicist
i would say there are not really yet any firm theories of (this kind of) multiverse. i'm not sure to which theories you refer? susskind's intuition i think is that one will find universes bubbling off from our own, but there's a lot more work to do yet i think. there's not much more i can say---the theories youre talking about need much more work to be well-defined. saying at this stage that these ideas will *never* be testable is premature. we don't understand them well enough, yet. physicist
PaV My point is that systems with random change can and often do generate patterned behavior. Patterned behavior is in not at all an indication of external design other then to say that a designer may have created certain rules for a system where random change can create patterned and ordered behavior. In short no external input is necessary for a chaotic system to create order and great complexity (CSI). ftrp11
Davescot in a sense, adding a cosmological constant to einstein's equations is the most conservative modification one can make. it *is* a modification to GR. Whether MJ can reference a better explanation i am not so sure. yes, the jury is still out on much of this---i'll definitely agree on that. physics is hard and we don';t know all the answers! if we did there wouldn't be much more physics to do physicist
MJ probably meant farther out from the galaxy instead of farther out into the galaxy. A simple typo anyone familiar with the issues should have recognized immediately. The recent unexpected discovery that the expansion of the universe is accelerating may due to gravity not acting how GR predicts at extremely long distances. Or there may be an undiscovered force of nature that was too weak to detect at short distances but becomes greater than gravity at long distances. Or it may be the cosmological constant is some infinitesimal bit larger than zero which I'm sure has Einstein rolling over in his grave as he thought it was the biggest mistake of his life to stick it into GR only to have it zeroed out by observation. Shrugging this off to a non-zero CC smacks of pencil whipping to me. Oh gee, the equation didn't work out quite right but if we just pull a constant out of our arse and adjust the value to fit the observations we can keep the theory. Uh, no. The jury is still out on this one. DaveScot
physicist, Unduly pessimistic? How so? In most of the multiverse theories the multiple universes are causally disconnected. That means, even in principle, there can be no communication without violating GR. We are not discussing technical hurdles. You may find this post interesting. Or at least Susskind's quote on the lack of testability for the landscape: "It would be very foolish to throw away the right answer on the basis that it doesn't conform to some criteria for what is or isn't science" Imagine if a pro-ID scientist made such a statement! David Heddle
there is also a lot of physics literature i could recommend for interested people to read.... physicist
A book I'd like to recommend: http://www.privilegedplanet.com/ Because it touches on some of the issues being discussed here. Bombadill
well, i think these are open questions in physics which people are trying to explore. nobody has the full answer right now. it might be argued that these ideas are currently `untestable', but i think it's unduly pessimistic to assume they will always remain so. physicist
ftrp11: I don’t understand what you mean by something being “brought about by mere chance” or something “exhibiting a true pattern.” The two are not exclusive of eacother. Well, this is exactly what ID is about. You might try reading some papers that Dembski has written. http://www.designinference.com/ PaV
physicist, What you might want to add, for completeness, is that that they (cosmologists) are exploring untestable (and therefore pseudo-scientific) multiverse theories, such as the string theory landscape, because they recognize that the only alternative to a multiverse-powered anthropic principle is design. There are either lots of universes, with different constants, and we naturally are in a habitable one, or the universe was designed. Both are untestable. Therefore, to the extent that the fine-tuned CC supports multiverses, it also, just as rigorously, supports ID. See, for more details, Susskind's Sophie's Choice. David Heddle
Hi David I'm fairly well aware of the issues surrounding the smallness of Lambda. It is not an easy discovery to explain. As you say though, cosmology is eschewing design in trying to find an explanation of this. I certainly wouldn't regard it as evidence for ID. all the best physicist
Sorry, comment #11 was intended for "physicist". David Heddle
If I'm reading this correctly, the analogy is that evolution is the equivalent of 'mere chance'. Why is this a good characterization of evolution? Isn't selection performed non-randomly? It seems to me that the way in which they explained an apparent pattern with natural, non-designed causes is very much like the way evolution explains the apparent patterns in life. Tiax
ftrp, Because it is 120 orders of magnitude smaller than expected, but yet it's not zero. If it were zero, or a little bigger, there would be no life. Cosmology, though eschewing design, is heading into the land of multiple universes to address this incredible fine tuning. David Heddle
ftrp i basically agree with you but there can be a distinction between dim-ness (conventional matter sources which our sensitivity isn't good enough to detect) and dark-ness (matter which interacts very weakly or not at all with photons). however, i agree from the observational POV people have thought about both possibilities. anyway, neither possibility is very mysterious. David Heddle---agree with you that MJ's comment makes little sense. why do you think the cosmological constant is important evidence for ID? physicist
MJ wrote: “Dark Matter” and “Dark Energy” are band-aids for the fact that the ToR breaks down the farther we get out into the galaxy. That comment makes no sense on many levels. First of all, ToR does not break down the further we get out in the galaxy. (ACtually we are far out in the galaxy, if you mean distance from the galactic center.) Secondly, these are quantities that span the universe, not just our galaxy. And, most perplexing of all, if my assumption that you are pro-ID is correct, is that dark energy, aka the cosmological constant, is currently ID's premier piece of evidence. David Heddle
Dark matter is just whatever matter in the universe that is not light emitting. From the viewpoint of the nearest star Earth is dark matter until at that local has equipment sensitive enough to detect it. Any gas in the universe not illuminated by nearby stars is also dar matter. Whether dark matter truly exists or not is not at all in doubt. The only problem is that for current theories to work there must be so much of it that we do not have a solid guess as to what it is all comprised of. ftrp11
PaV I don't understand what you mean by something being "brought about by mere chance" or something "exhibiting a true pattern." The two are not exclusive of eacother. ftrp11
oh and i'll add to that Ia supernovae evidence for dark energy/lambda physicist
M J Gr certainly is not the final story. but whether it breaks down in the ways you mean i'm not so sure. since you haven't really explained what you mean it's difficult to know, but i'd be interested in what theory you know that consistently explains galactic rotation curves, spectrum of primordial fluctuations in CMB etc without dark matter physicist
"Dark Matter" and "Dark Energy" are band-aids for the fact that the ToR breaks down the farther we get out into the galaxy. M J
PaV "It’s sort of like an ‘Unmoved Mover’: we don’t see it; can’t detect; don’t know its nature; yet we can detect its effects in our world." I think you overstate the case against dark matter as `real' physics here. there is quite a lot of evidence for dark matter from astronomical observations. i could go into it in detail. as to your specific thoughts above: whether we can `see' something just depends on the strength of its interaction with photons. there's nothing too mysterious there. as to detection, well apart from the gravitational detection in astronomical observations, I also hope we will see direct evidence for such new particles at the LHC in the next couple of years. i would wait and see before deciding that `we can't detect' it. i'm also not sure what your last comment really means. if we can detect its effects in our world, that is detection, right? physicist
ftrp11: You seem to miss the point. Nature obviously caused this 'plane' to exist; no one disputes that. But this was an unexpected structure. When the scientists began trying to understand it, they had to distinguish between this being an object brought about by mere chance, or that it was something exhibiting a true 'pattern' (ID is afterall about 'pattern' detection). They easily dismissed it as chance and now attribute it to 'dark matter'. Think about that: 'dark matter'. They don't know what it is; they don't even know if it really exists; yet, based on the 'pattern' they see, the attribute this planar phenomena to 'dark matter'. It's sort of like an 'Unmoved Mover': we don't see it; can't detect; don't know its nature; yet we can detect its effects in our world. Does this sound familiar at all? PaV
"Seeing regularities in the midst of a huge number of other possibilities is, really, suggestive of something other than chance. Seems like scientists do it all the time. In fact, it appears easy to do. Keep reading." Nature causes order and regularity all the time. Is it divine providence that hurricanes can make such tight spirals or tornadoes make perfect funnel shapes? OR when geology creates right angles in rock creating the appearence of steps? How do planets for such neat rings. Regularities are not peculiar when they are the only possible outcome given the forces and material involved.. ftrp11

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