New Gravity Theory Dispenses with Dark Matter

Darkness Matters writes "According to New Scientist, a theory of modified gravity, which has no need of dark matter, has just explained why the Pioneer 10 probe is 400,000 miles off its expected course as it leaves the solar system. It sounds pretty convincing, although in dispensing with dark matter, they've had to utilize the theoretical particle, called a graviton, which appears from the vacuum of space wherever stars are densely packed, making gravity stronger."

Comments

Gravitons are not a new concept

[csoto]

This has been around for years. If a hypothesis involving gravitons is explained by experimental evidence, then this hypothesis could be elevated to theory.

Besides, didn't we use to shoot gravitons at that loud squiggly thing in Yar's Revenge?

Re:Gravitons are not a new concept

[G3ckoG33k]

Well, as the article states "it has yet to pass the most crucial test - how to account for the afterglow of the big bang".

So, it won't be the theory you are after until some more time.

Re:Gravitons are not a new concept

[MustardMan]

However, we're still left with the age old question: If gravity is manifest as a particle, why can't we shield against it?

There could be lots of reasons for this. The mechanism certainly isn't the same, but as an example of a particle which cannot be shielded, you need look no further than a neutrino, which can pass through the entire Earth.

Re:Gravitons are not a new concept

[Anonymous Coward]

If gravity is manifest as a particle, why can't we shield against it?

Just because we don't know how to do something, it doesn't mean that it is impossible.

Please be real! :D

[SalsaDoom]

Man, I hope this is real so much. I've always hated dark matter. You know what dark matter reminds me of? Aether. The whole idea of dark matter reminds me of a stupid hack -- which I suppose you have to deal with when it comes to topics like physics now and then.. its not like we can just go and look so readily ;P

Anyway, these "Gavitons".. I think I've had them in computer games for a while now, its about time we 'discovered' them. Aethe-- I mean Dark Matter was such a cranks idea anyway... anything has to be better then "OOoooh! There must be... some.. uh, invisible undetectable matter.. that uh, has mass. But you can't see it, because.. its dark! yeah thats the ticket." Given an unlimited choice of possibilities I could have came up with something better, and it probably would have been about as scientifically valid too. :)

Hurray for gavitons! Prepare the graviton pulse cannons! :D
--SD

Re:Please be real! :D

[drxenos]

I think Occam's might not be of use here. One theory has dark matter, the other has a new particle. I think it might be a wash.

F for reading comprehension

[TripMaster Monkey]

Nearly right : The theory posits that gravitons are created by all (massive) matter, it's just that near densely packed stars the effect is more significant.

Actually, no. The point the atricle is making is that the effect increases near large concentrations of mass at a rate greater the simple total mass would predict.From TFA:

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.

Plain wrong : From TFA "critics point out that MOND cannot explain the observed masses of clusters of galaxies without invoking dark matter"

The article isn't about MOND, it's about the scalar-tensor-vector gravity (STVG) theory. MOND was just mentioned as a competing theory...a theory that couldn't adequately explain the behavior of galatic clusters or the Pioneer spacecraft.

Testable with planetary motion?

[G4from128k]

If gravity isn't quite what it seems to be in terms of strength versus distance, then studies of planetary systems should show the effect. The relationship between orbital radii and orbital periods (and orbital path) would not be quite consistent with the 1/r^2 rule for Newtonian gravity. Admittedly the distance and mass scales of a our planetary system are far smaller than the galactic scales discussed in the theory, but our ability to make extremely precise measurements of planetary distances and orbits should compensate for that.

Re:Gravitons?!

[DrFrob]

The real problem with this article is that it was published in NewScientist, which, as I discovered as an undergrad, is often full of incredibly exciting ideas supported by very little evidence and frequently go nowhere.

Uhh - Action at a Distance?

[mosel-saar-ruwer]

The post makes it sound like suggesting that gravitons exist is outlandish... but this is rather accepted.

IANAP [or a Cosmologist], but Pioneer 10 is pretty damned far out there at this point. So far, in fact, that it must take, what - several hours? several days? - for something travelling very, very fast [as in "The Speed of Light"] to get from here [that big fat gravity source called "our sun"] to there [the Kuiper belt, or wherever the hell Pioneer 10 finds itself these days].

Is not one of the big problems with "gravitons" that gravity appears to act more or less instantaneously at great distances? And isn't that a little troubling from the "Action at a Distance is Big No-No" point of view?

Or does the theory of "gravitons" come with some fancy-schmantzy geometric/topological intricacies which allow for the possibility that Pioneer 10 isn't quite as far away as we think it is?

Heim Unified Field Theory

[scorp1us]

The Heim Unified Field Theory or here is astonishingly accurate theory. Derived from Eenstien's thoery of relativity he postulates 12 (6 major) dimensions. He also postulates gravitophotons. It has been very suceesful in:

• determining mass of most fundamental particles to experimental accuracy (the others are damn close)
  
• Explaining the problem of entropy and the big bang. (In his model matter forms after expansion begins, so the laws of thermodynamics are consistent)
  
• explains the effects we currently attribute to "dark matter" without needing actual matter.
  
• brings relativity and quantum mechanics into accord.
  

I highly suggest you read up on it if you like physics.

Re:when will it stop

[thrillseeker]

To be fair to the original poster, New Scientist has been going downhill very fast for some time. It is now basically a science tabloid. Most of the lead articles are about highly speculative almost-science.

To exerimentally verify this go and buy one copy of New Scientist and one copy of Scientific America. Compare.

Can't. Quit reading SA after they started publishing thinly vieled political hacks instead of science articles.

It's only a theory

[smooth wombat]

It's only a theory folks. We shouldn't be teaching it because it hasn't been proven. It's not a fact.

(For the humor impaired I'll give you a few moments to let the words sink in)

Re:It's only a theory

[Alsee]

So, continue to chastise the religious folks for believing in something that they have never seen.

No, I do not think that is a fair accusation.

His ridicule did not target religious folk, and it certainly did not target anyone for for believing in God. His comment in no way chastied the MAJORITY of religious folk, nor did it chastize the majority of Christians, and it did not chastize the official position of the Vatican. His comment targeted a minority group who happen to also be religious, a minority group going counter to mainstream majority Christians, and it targeted them for very specific reason of bad acts that are independant of belief in God.

Seems science puts a lot of weight on things no one has ever seen or proved as fact.

Science puts an amount of weight on things based on the amount of testing and confirmed predictions.

For example Dark Matter Theory has some pretty hefty weight. It is by far the leading theory in its area because it has made quite a few predictions that have been extensively tested and confirmed. It has explained more and had more confirmed predictions and has fewer problems and unexplained issues than any competing theory in the field.

And while "leading theory" is a fairly hefty position, it still falls far short of earning the full weight of "established/accepted science" as accepted by over 99% of PhDs and professionals in its area, far short of the title "indisputed foundation of its field". That is a far weightier level, a level of weight that is only earned by theories that have undergone staggering amounts of testing and which have make a large number of predictions that have been exhaustively and conclusively confirmed, theories with no signifigant contrary evidence, theories where there is *NO* known usable countertheory.

For example Relativity and Quantum Mechanics and Evolution all fall in that catagory. Each one is accepted by over 99% of the PhD's and professionals in its area. Each one is considered the very foundation of its area of science. Each one has made many many predictions, and they have been exhastively tested and conclusively confirmed with staggering mountains of evidence supporting them. None of them has any known signifigant counter evidence. There is no known theory that even comes close to competing with them in their area.

If you think that Relativity or Quantum Mechanics or Evolution conflict with God, then you are a scientifically illiterate and religiously illiterate fool deserving of chastizement. The position of mainstream majority scientists, the position of mainstream majority Christians (two groups with substantial overlap by the way), the official position of the Vatican and as explicitly and repeatedly stated by multiple Popes, is that there is no conflict between science and religion, no conflict between any of those areas of science and God.

The people who rejected and attacked Galileo because they thought there was a conflict between his science and God, they were fools and they deserved chastizement. And anyone today who says that there is a conflict between some feild of science and God is equally a fool, and equally deserves chastizement. That goes equally for either side. Anyone who's a scientist and happens to be anti-religion is a fool if they claim there is a conflict. Anyone who is religious and happens to be anti-science is a fool if they claim there is a conflict.

If someone with no education in Quantume Mechanics and no understanding of what it actually says and means, if that person were to claim that Quantum Mechanics was wrong and that 99+% of expert PhD professional physicists were all wrong and stupid and that they somehow mysteriously overlooked all the simple and obvious "counter proofs" that they come up with to prove Quantum Mechanics wrong and impossible, what do you think the reaction would be? Someone with no education in the field having the delusion to claim that a half million or so genuine experts and PhDs and professionals rep

Re:read your augustine

[taylorc209]

The "After all, if something couldn't come from nothing how did God come about?" question is not a valid one. For an indepth explanation please read augustine, aquinas, c.s. lewis, I think descartes version of the ontological argument even hits on this, but really any book on christian apologetics will help you out. A very rough sketch of the arguement is that God, by definition, needs to exist without being casued. Everything in this universe needs a cause, so what caused it? For Aristotle it was the unmoved mover, for creatonists it is the Christian God. That which necesarily exists without needing to be caused. That is one of the attributes of the creationist God (or really anybodys God). To say what caused God, ok say x caused God then what caused x? It goes on forever eventually something must exist that needs no cause. That something is God. While I and many other christians don't agree with the creationists attack on evolution, it is a logical fallacy to commute one wrong step with all of christianity being false. As I can't prove it in depth in a post on /. please refer to any apologist, c.s. Lewis is my favorite for a more conclusive step by step account.

your friendly neighborhood philosophy student

Re:Dark Matter? Gravitons?

[Obvius]

I read physics at university. An optional Third year course was 'General Relativity'. In the little booklet they gave us to help in choosing what courses to 'major' in (it was an english university), there was an asterisk next to 'General Relativity', as well as 'Cosmology' as a matter of fact. The asterisk denoted 'mathematically rigorous - to be considered only by students with particularly strong mathematical backgrounds'. My friends and I didn't take it - we did things like Computational Physics and Astrophysics instead. In fact, one afternoon, for a laugh (crazy guys that we were) we sat in on a General Relativity lecture to see if we could even keep up. It was a thirty minute lecture on 'Aphelion Procession Using the Scwarzchild Geodesic'. We didn't stand a chance - ball-breakingly tensor analysis. My point is, at that time I knew a hell of a lot more physics than your average guy in the street and I didn't have a clue what was going on in that General Relativity lecture. I read around, spoke to people smarter than I was, spent a fair bit of time trying to get my head around General Relativity I didn't even scratch the surface. And I was a straight-A student back then. I just don't think there exists such a thing as a layman explanation of our understanding of gravity. That other splendid bugger Dr Richard Feynman once said something like 'If a theory can't be reasonably well explained in a single undergraduate lecture then we don't really understand it at all.' It may be that we don't really understand the theory of General Relativity - maybe there is a far more elegant theory explaining gravity that could be explain gravity in simpler terms. For certain, though, that theory does not currently exist. It's a shame, because like you I was always frustrated by the absence of a simple answer to 'How does gravity work?', Why is it always attractive and never repulsive? Some things are just really, really difficult to model and the only models we have are 'mathematically rigorous'. In the words of JBS Haldane 'The universe is not only stranger than we imagine, it is stranger than we can imagine'. http://en.wikipedia.org/wiki/Richard_Feynman http://en.wikipedia.org/wiki/General_relativity http://en.wikipedia.org/wiki/Tensor_analysis

Re:read your augustine

[Cadallin]

Descartes argument is different, and perhaps even weaker. Your argument is essentially:

1. God needs to exist without being caused (P, proposition)

2. Therefore, God exists without being caused (P, same proposition again)

You don't really even have an argument there, you're just making an arbitrary fact claim with no evidence, and no argument. You can expand this and make it more fancy, but it's always reducible to this fact claim. Arguably the greatest mistake is fact claim "Everything needs a cause." Which is either correct, or incorrect, if it is correct, then god can't be uncaused, and therefore, accordingly to your logic the universe can't exist (deus ex machina not being allowed in proper logic), if it is incorrect, then god isn't necessary for the universe to exist anyway. God may exist, but by Occam's razor, it is the simplest explanation that it does not.

Re:Here we go again

[ave19]

When a theory like dark matter has amassed evidence in its favor over a period of decades, it takes a lot to overturn it.

Don't forget, though, that as long as ANY nook or cranny remains uncovered by the theory of Dark Matter, there is room for a replacement. Dark Matter has been predictive, but there is still a problem with it, none has been detected, and as we search for it and fail, we make the remaining possible types of it more and more exotic. The whole situation reminds me of the search for ether. As they searched, they found that the ether, what ever it was, must have certain properties. They really thought they were making progress, too, until some of those properties began to conflict with each other. The situation seemed impossible, because it was. There is no ether. Someone is going to get a Nobel prize for saying: "There is no Dark Matter" and proving it.

Actually...

[brian0918]

"More of the 'uh... well, it went away when you came in. It's only around when you're not looking. And it knocks things over when I'm the only one in the room' variety..."

This sounds more like the work of a quantum physicist.

Re:at first I saw...

[gid13]

Are you MAD? That was the greatest midway ride in the history of mankind!!!

Re:Here we go again

[radtea]

First off, dark matter, even if it ultimately turns out to be wrong, is not a stupid idea;

I agree--dark matter is not even an idea. It is a family of ideas. They are all reasonable ideas. But having watched the growth of dark matter theories in the past twenty years--hot dark matter, cold dark matter, warm dark matter, MACHOs, WIMPs, etc ad nauseum--I think there is some justification for a degree of skepticism regarding any dark matter theory.

All I ask of proponents of any dark matter theory is that they specify:

1) Type: baronic or not?
2) Interaction: parameter space dimensions and constraints (that is, is it weak, gravitational only, exotic, and if so what are the model parameters and how are they constrained)?
3) Scale: stellar, galactic, local group, large scale galaxy distribution or CMB?

When people talk about dark matter as if it was a single theory rather than a family of hypotheses, like this guy does in the article:

"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"

it is reasonable to point out that this is marketing, not science, and that there is nothing like a consensus with regard to the answers to my questions above. This does not mean that dark matter is a stupid idea. It means that a family of theories with a very large number of free parameters does not make a very satisfying explanation for anything.

Re:Wouldn't a graviton have negative momentum?

[Anonymous Coward]

Exactly. We don't come to slashdot to discuss interesting theories and try to better understand them, we come to slashdot to show our own superior knowledge and insult or otherwise spit upon those who aren't up to our level. Thank you Breakfast Pants, for making it clear that non-experts are not welcome here.