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.

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

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.

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: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

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.