Do We Need a New Theory of Gravitation?
Written by Nancy Atkinson
Draco satellite dwarf galaxy. Credit: Mischa Schirmer, University of Bonn
A group of physicists say that the distribution of satellite galaxies that orbit the Milky Way, as well as the apparent dark matter within them, presents a direct challenge to Newton’s theory of gravitation, as the galaxies are not where they should be. “There is something odd about their distribution,” said Professor Pavel Kroupa from the University of Bonn in Germany. “They should be uniformly arranged around the Milky Way, but this is not what we found.” Standard cosmological models predict the presence of hundreds of these companions around most of the larger galaxies, but up to now only 30 have been observed around the Milky Way. The physicists say that Newton's theory of gravitation should be modified.
The astronomers from Germany, Austria and Australia looked at the small dwarf galaxies that orbit the Milky Way and discovered that the eleven brightest of the dwarf galaxies lie more or less in the same plane – in a kind of disk shape – and that they revolve in the same direction around the Milky Way (in the same way as planets in the Solar System revolve around the Sun). Some of these contain only a few thousand stars and so are relatively faint and difficult to find.
Professor Kroupa and the other physicists believe that this can only be explained if today’s satellite galaxies were created by ancient collisions between young galaxies. Team member Dr. Manuel Metz said, “Fragments from early collisions can form the revolving dwarf galaxies we see today, but this introduces a paradox. Calculations suggest that the dwarf satellites cannot contain any dark matter if they were created in this way. But this directly contradicts other evidence. Unless the dark matter is present, the stars in the galaxies are moving around much faster than predicted by Newton’s standard theory of gravitation.”
Metz added, “The only solution is to reject Newton’s theory. If we live in a Universe where a modified law of gravitation applies, then our observations would be explainable without dark matter.”
With this evidence, the team share the convictions of a number of groups around the world who believe that some of the fundamental principles of physics have been incorrectly understood. If their ideas are correct, it will not be the first time that Newton’s theory of gravitation has been modified. In the 20th century it happened when Einstein introduced his Special and General Theories of Relativity and again when quantum mechanics was developed to explain physics on sub-atomic scales. The anomalies detected by Dr. Metz and Professor Kroupa and their collaborators imply that where weak accelerations predominate, a ‘modified Newtonian dynamic’ may have to be used. If the scientists are right then this has far-reaching consequences for our understanding of the Universe we live in.
The two studies will appear in papers in Monthly Notices of the Royal Astronomical Society and the Astrophysical Journal.
Source: RAS
Filed under: Physics, galaxies
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April 21st, 2009 at 6:25 pm
That's an interesting idea, but I like how they didn't put forward that their computations might be incorrect, rather than the theory of gravity. Regardless, it's always nice to see some progress.
April 21st, 2009 at 6:41 pm
I'm not really all that good with science and math, and my memory is quite faulty, but I was under the impression that Newtonian gravity was disproved years ago and supplanted by Einsteinian gravity, which behaves much differently on the larger galaxy-wide scale than does the more simplistic Newtonian equations. (Though both theories are said to produce similar results on the smaller scale of our solar system.)
Or perhaps I imagined that.
April 21st, 2009 at 7:19 pm
Damon Smith Says:
April 21st, 2009 at 6:41 pm
No no – you're quite right. GR is the 'correct' theory of gravity, in so much as it has made many subsequently verified predictions of new effects and has never had a counter example discovered that has disproven it (despite the claims of whack-jobs). When they use the term Newtonian in this article, I believe they are referring to the 'inverse square' character of the force. MOND (modified gravity) proponents assert that over large spatial scales, gravity deviates from inverse square causing an effect that could also be achieved with the presence of 'dark matter'. GR is also an inverse square theory, and so if MOND were to be correct then both theories would need modification. MOND is still very young though and has it's own significant shortcomings, despite yielding a seemingly valid prediction in this case.
There are a lot of big 'ifs' around this work it would seem. There is so much about galactic dynamics and formation that we do not understand that this study, while a noteworthy result, would still be impossible to put into it's proper context in my opinion. In the end, any theorist worth his salt can fit a theory to observation if there are enough free parameters involved an assumptions made. It's all about making new predictions that are subsequently verified.
PS – Let me guess Oils – your theory predicts precisely 30 orbiting dwarf galaxies? Maybe a few more in light of potential future observations? Kepler predicted this in the year 1595?
April 21st, 2009 at 7:26 pm
This looks like Mordehai Milgrom's MOND again, another attempt to disprove dark matter. My understanding is that the consensus is heavily against MOND right now, based on images of colliding galaxy clusters taken in multiple wavelengths. Sky and Telescope had an article on this a few months ago.
April 21st, 2009 at 7:34 pm
How can these astronomers see a conflict with the distrobution of these galaxies with respect to GR when they in all likely hood, quite literally, can not see all of the orbiting galaxies? There question has a lot of poorly supported assumptions.
However, the stars that are moving a lot faster than they "should" be seems to be a lot more disturbing. I guess our understanding of galactic formation, GR, or both needs some work.
April 21st, 2009 at 8:00 pm
Gravitation doesn't need to be modified at all: it's the perfect hypothesis for unthinking morons and mathematical ignoramouses.
Gravitation needs to be abandoned entirely.
Ever heard of electricity and magnetism?
April 21st, 2009 at 8:03 pm
MOND — yuck, I'd hate to see that. If that is how the world works then things are inelegant in the extreme.
Gravitation needs to be rescripted to fit with quantum mechanics. I also think for cosmology gravitation (general relativity) needs to be modified. Currently the curvatures of spacetime is determined by connections between locally flat regions. I think this should be extended to conformally flat regions.
I am not a galaxy person, but these phenomenological calculations may have some input or boundary/initial conditions that are wrong. These types of models are very messy and run numerically. Some model dependent input may be at fault here.
Lawrence B. Crowell
April 21st, 2009 at 8:04 pm
The article states that this modified theory would basically do away with dark matter. How can this be when there is other non-gravitational evidence of dark matter, e.g. the cosmic background radiation, where the WMAP data enabled scientists to calculate the proportion of baryonic matter, dark matter and dark energy in the observable universe. It doesnt seem very obvious how this modified theory of gravity would explain the CMB data.
From memory there was also the indirect evidence of dark matter seen by the high speed interactions in the bullet cluster: chandra.harvard.edu/press/06_releases/press_082106.html
Any ideas?
April 21st, 2009 at 8:08 pm
Joe,
For your information microwaves are electromagnetic and have more to do with invisible pink unicrons than they do with gravitation.
Dark Matter is 99.99% of Meinong's Jungle, whereas electric plasma is 99.99% of the visible universe.
April 21st, 2009 at 8:09 pm
This does indeed sound like a MOND-based interpretation of gravity. Any links to peer-reviewed (free) papers?
April 21st, 2009 at 8:11 pm
Lawrence,
"Currently the curvatures of spacetime is determined by connections between locally flat regions. I think this should be extended to conformally flat regions."
Can I borrow your tinfoil hat so I can determine the curvature of spacetime?
April 21st, 2009 at 8:13 pm
Jon,
"Any links to peer-reviewed (free) papers?"
See here: http://www3.interscience.wiley.com/journal/114107477/abstract
April 21st, 2009 at 8:32 pm
Sorry, i should have clarified my question…
Does anybody who knows what they are talking about have any ideas?
April 21st, 2009 at 8:47 pm
I'm going to hazard a guess that 1) we are more or less correct about dark matter and that 2) the theory of gravity will likely not need any modification to "explain away" dark matter. Gravity can be measured very precisely here on Earth (and elsewhere), and if there was some kind of "fudge factor" going on that would invalidate Newton's general model it would be detected by now.
Now, dark *energy*, on the other hand… (but that's a topic for a different thread).
April 21st, 2009 at 8:51 pm
Dave,
1) We are correct that Dark Matter is a myth.
2) The so-called "theory" of gravitation is also a myth.
3) Dark energy is yet another myth.
Wow. 3 myths and yet they call it science.
April 21st, 2009 at 9:01 pm
Coincidentally, an interesting paper discussing a possible alternative to both Milgrom's MOND and dark matter appeared on arXiv yesterday: "A Realistic Cosmology Without Cold Dark Matter" (arXiv:0904.2935v1 [astro-ph.CO] 20 Apr 2009). Paraphrasing the authors, they present a model which provides a general framework which can potentially solve the problems of CDM on galactic scales and of MOND on larger scales. They claim that It could also be generalized to include dark energy in a way such that all the phenomena of CDM, MOND and dark energy are related to one parameter which is the single mass scale introduced in their model.
Like most responsible theoretical work, these authors do not claim to have discovered some magic "truth" but they do suggest an approach towards solving a possible problem and their approach may deserve closer consideration.
April 21st, 2009 at 9:59 pm
Data coming in from deep field studies suggests that we know less about how galaxies formed than we thought. The fact that there are fewer dwarf galaxies than expected I think is not significant with regards to the nature of gravity and simply deomnstrates our ignorance of galaxy formation theories. I do agree that the location of these dwarfs in a single plane and their uniform rotation suggests they are products of past interactions with our galaxy. As such, I have a hard time arguing with the point that they should have been stripped of their dark matter and not revolving around the galaxy so fast. I think it is easier to argue that these dwarves managed to hold onto some of their original dark matter or accumulate more of it over time following their interaction with our galaxy. Of course the discovery of evidence proving the existence of dark matter would be most helpful here and end the speculation that it is a convenient invocation holding up long held standard cosmological assumptions based on an ever aging data set.
April 21st, 2009 at 11:13 pm
Oooooh – Oils is all fired up! So many assertions with so little evidence in so little time taking up so much space! He's building to a crescendo! He's gonna pop!
April 21st, 2009 at 11:26 pm
"My understanding is that the consensus is heavily against MOND right now,"
I believe you are right. It does make some seemingly accurate predictions in some cases, but I believe the consensus is that it is either not viable or needs drastic unknown modifications.
"MOND — yuck, I’d hate to see that. If that is how the world works then things are inelegant in the extreme."
Agreed. I'd be pissed at the universe if MOND turned out to be the case. Although, it seems everything in cosmology is getting increasingly inelegant at the moment. That's a good thing in my book, because it is usually not too long after such points that a great unifying idea comes through and kicks some arse, lights some fires and just generally shapes everything up. We're bumping around the room in the dark with a candle, but it seems that we're moving towards the light switch.
April 22nd, 2009 at 12:47 am
Astrofiend,
"I’d be pissed at the universe if MOND turned out to be the case."
Well if you'd be pissed about it, then it can't possibly be true…=)
April 22nd, 2009 at 12:55 am
i'm no expert on anything space-related.
Everything i know or think, i learned through googling and reading (the comments) this site.
But when you think about the following:
-The earth has a core, it rotates round this core. (i don't know if this is something most planets do)
-A solar system, rotates round the sun.
-A galaxy, rotates round his supersized-sun or blackhole.
-What if galaxy's also rotate something bigger.
Couldn't did effect the law of gravitation?
April 22nd, 2009 at 2:05 am
If Halton Arp is right, these dwarf galaxies are are in fact 'offspring' of the Milky way. They have been ejected from it when it's nucleus was active.
Jets from the galactic center shot out matter with zero mass at the speed of light that then condensed as the
ejected matter gained mass by interacting with its surroundings (Mach's principle)
April 22nd, 2009 at 3:03 am
Hi! the first question that cropped up is that we are still under a very big assumption that MW is the centre of this group….And thats y we find the others to be distributed in an unexpected way….What if there is a more massive galaxy mainly made up of dark matter, so that the visible matter is less and makes us assume that it is a dwarf but which is ineffect the centre of this group!! is it not possible to find that????
April 22nd, 2009 at 3:19 am
He is not.
April 22nd, 2009 at 4:41 am
Taking the assumption that the galaxy should have the same qualities as our solar system is not wrong, but the scale real has to be thought of correctly. We observe that the rings of Saturn are affected by the moons. Resonance causes certain rings to evenly form and cause spaces between those rings. Look at the kuiper belt and the distributions. I am sure that at one time long ago, there was disarray — voids where we would expect to find clusters of debris. The scale of the MW is a whole different ball game. Time for one thing. The farther we go in space, the slower time passes relative to us here. We are seeing the young galaxy where our solar system is aged and matured.
If the MW was Earth and the Andromena galaxy was Mars, why is it in a direct path for us. Our local group is still on a creation scale. Obviously our galactic orbits are not complete.
And yes I believe there is a web of special relativity about the whole local galaxy cluster that can affect distributions in our galaxy the same way moons affect the rings of Saturn.
As far as dark matter, we have not found what it is. The scale of this may even be in our solar system, but undetectable, or more accurately so minute that it is creating no substantial affect.
This is only my opinion but we (the MW galaxy) may end up like the Main belt eventually — in one large cluster debris in a supergroup.
Have a nice day.
Todd
April 22nd, 2009 at 6:04 am
This is a rather weird article. It talks about specifically Newtonian gravity, not mentioning MOND by name, nor mentioning general relativity either, but while still talking about galactic gravitational reactions. That in itself shows me that either we're not being told very good details about the specifics of the simulations, or that those simulations aren't based on the laws of physics as we know them. It's also highly unusual to see a comment like:
'Metz added, “The only solution is to reject Newton’s theory. If we live in a Universe where a modified law of gravitation applies, then our observations would be explainable without dark matter.”'
In most scientific writing I've seen, the phrase "the only solution" can come up when literally all other solutions are proven to be unreliable, and that all other possible solutions have been tested. I find this latter assumption unbelieveable. The phrase "one possible solution" seems much more appropriate.
April 22nd, 2009 at 6:10 am
Here's an alternative idea….
Maybe there are two sorts of gravity, one is the force of attraction to the center (the one that we know of) and the other the force of attraction to, say, outer space.
Lets call them Gf (f for centrifugal) and Gp (p for centripedal)
When you think about it, the edge of the Universe is being attracted into the region that it does not yet occupy. Maybe some particles are subject to Gf and will have an affinty with this boundary.
This could be an effect ot the spin of the original quantum fluctuation that (it is theorised) created our universe. Cerntainly the sprites above electical storms are departing straight up!
April 22nd, 2009 at 6:30 am
@ Joe, I think what they're saying that if MOND is invoked, DM is not required to hold together galaxy clusters nor is it needed to explain flat rotation curves in galaxies. I don't know enough about the theory to explain the its effect on the CMB observations. The 'Bullet Cluster' paper entitled " A direct empirical proof of the existence of Dark Matter" by Clowe, et al can be found here: http://arxiv.org/PS_cache/astro-ph/pdf/0608/0608407v1.pdf . This 2006 paper is indeed a modern 'classic' that launched a flurry of research on DM in general and this merging cluster in particular. I've even read at least one paper recently giving a MOND interpretation of observations of the Bullet Cluster (where are the papers from EU/PU/PC 'scientists' on their interpretation of what's observed in the Bullet Cluster [1E 0657-56]?). @ Oills, thanks for the link to the abstract, but I couldn't find a free version of the PAPER you referenced. Can you provide a link to the paper, seriously, because I do remember seeing something on this topic and would be interested to read the argument they put forth?
April 22nd, 2009 at 6:53 am
All of the 'proofs' of Dark Matter involve very distant events and assumptions about how we should interpret the signals of these events.
All of the more local scale observations, including this one in our own galaxy, have provided null results for possible dark matter attributes.
We can reject the Dark Matter hypothesis because the best evidence is inconsistent with the Dark Matter solution.
This does not really support MOND as a solution – Mond is a fairly simple mathematical treatment that models stellar flow in many situations.
April 22nd, 2009 at 8:03 am
@ Andrew, I must agree with all the points you brought up in your last post, especially the Metz quote. Guess we'll have to wait to read the full paper because this news release seems short on details, as other posters have also pointed out. I also concur with Astrofiend when he states "Although, it seems everything in cosmology is getting increasingly inelegant at the moment. That’s a good thing in my book, because it is usually not too long after such points that a great unifying idea comes through and kicks some arse, lights some fires and just generally shapes everything up. We’re bumping around the room in the dark with a candle, but it seems that we’re moving towards the light switch." I just hope this happens in my lifetime!
April 22nd, 2009 at 9:42 am
I think all theories should be able to make way for something new if it fits the facts better, isn't that what science is all about.
April 22nd, 2009 at 10:53 am
Joe…
Basically, we would have to toss out the standard model as we know it today, and revamp it.
The SM as it stands today has gravity being constant. If we take away dark matter, and believe gravity isn't constant in all states with all matter, this would answer the question.
Problem is… all our current proof shows gravity is a constant.
So you have 2 types of individuals. Those who believe in dark matter, and those who believe gravity isn't constant.
Now and then, a little revolution with the cosmological standard model is a good thing!
April 22nd, 2009 at 10:57 am
Glad to see more comments reffering to plasma and magnetism, that's the future of cosmologic breakthroughs.
Newtonian (and Einstein fabric) gravity only works locally (and is by the way only a pushing force, not pulling). Time to leave Big Bang and dark matter and other exotic theories that only generate more silly questions than useful answers.
April 22nd, 2009 at 11:58 am
@ Dirk:
Since when is gravity a pushing force? Unlike electromagnetism it is ONLY pulling and nothing else – that is its advantage!
April 22nd, 2009 at 12:08 pm
I agree with Dirk : quote Time to leave Big Bang and dark matter and other exotic theories that only generate more silly questions than useful answers unquote. He is also right that there is no pulling force.
No one can explain why matter attracs matter. In m.o. there is only one "force" in the universe and that force pushes. I call it a competition force (ousting force)
April 22nd, 2009 at 1:11 pm
spoodle58 says "I think all theories should be able to make way for something new if it fits the facts better, isn’t that what science is all about." I could not agree more. Just 100 years ago, a debate raged as to whether the Milky Way Galaxy consisted of the whole universe. Better data came along that showed our galaxy was only one of many. So the new view of the universe was incorporated into mainstream astronomy. I think the problem arises when someone takes a stand on a theory that appeals to them and will not consider it mistaken or incorrect no matter how many observations disprove it. Generally reasonable people will fess up and abandon their pet theory if observation after observation shows it to be flawed in some manner. I think this is what did in Arp , Hoyle, and Burbidge.
April 22nd, 2009 at 1:24 pm
Dr. Flimmer,
"He's not."
You must be blind.
April 22nd, 2009 at 3:56 pm
You know, you really could swap out OilIs' quotes with ones from Gene Ray, and the content of his posts would remain just about as informative.
April 22nd, 2009 at 4:35 pm
"Well if you’d be pissed about it, then it can’t possibly be true…=)"
Of course it could be true. I'm under no illusion that the universe really cares what I, or indeed anybody else, thinks. Unless the Strong Anthroptic Principle holds, of course. Like hell it does though.
Anyway, MOND seems way ugly at the moment. Ergo, I'd be pissed.
April 22nd, 2009 at 9:23 pm
Dirk:
DrFlimmer:
DrFlimmer, I think that this is what Dirk is thinking of.
April 23rd, 2009 at 10:00 am
Superconducting levitation anyone? How about superconduting levitation coupling to a gravity wave effect?
http://www.prweb.com/releases/2006/03/prweb364473.htm
We've seen superconducting fields levitate objects. Early experiments were limited to the levitation of magnets.
Several years ago, researchers using a semiconductor plate formed in a high gauss mag. field found that at superconduting temperatures they were able to create a levitation 'beam' effect when current was applied opposite the plate's mag. alignment. That beam apparently propogated infinately and also worked (levitated) on non-magnetically aligned matter. When the current was applied in an opposite direction, matter in the beam became heavier!
Not unlike 'cold fusion' , newsbrief's trumpeting this advance, were then discredited, and information about this effect 'dissappeared' from the web.
Wary interesting that….
And when we consider that superconducting at high temperatures in the Earth's core IS a possibility, where does that leave the theory of gravitation?
Cold fusion in the outer planets IS a distinct possibilty – I like Jupiter and Saturn as examples because we've been there and have seen unexplainable EM field discharges.
Otay… now, how about 'cold fusion' powered mag. fields around superconducting planetary or even stellar core materials.
Something to think about anyway… Oui?