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Survey Finds No Hint of Dark Matter Near Solar System
Eponymous Hero writes "Does dark matter exist or doesn't it? It seems these results don't shed as much light as we'd hoped. 'Moni Bidin says he's not sure whether dark matter exists or not. But he says that his team's survey (PDF) is the most comprehensive of its type ever done, and the puzzling results must be reckoned with. "We don't have a good comprehension of what is going on," he says.' This has the smell of a Neutrinogate scandal, but at least we've been warned about the shoulder shrugging. 'As an example, Newberg notes that the researchers assumed that the group of stars they examined were smoothly distributed above and below the plane of the Milky Way. But if the distribution turns out to be lumpier, as is the case for stars in the outer parts of the galaxy, then the resulting calculations of dark matter density could be incorrect. Flynn agrees that there are a number of ways that the method employed by Moni Bidin and his co-authors "could get it wrong."'"
I've never liked the theory of dark matter/energy. It always seemed to be a fudge factor thrown in to make the current theories work with what is observed. Astronomers have had good luck with that in the past, identifying planets and black holes based on gravitic effects, but they might have to a whole new approach to describe larger scales like this.
I truly hope it isn't dark matter. I *want* there to be a new theory. We'd end up learning so much more from it!
You would think that with a planet named Uranus there would be some somewhere. Oh did I really type that? My inner child is acting out again.
We have seen its effect on the solar system but I don't think we have any really evidence for what exactly Dark Matter is?
Is it matter? is it particles?
We have theories on what Dark Matter is, but those theories could be completely wrong.
So dark matter, as we know it, might not exist, all we know is that something is causing the effects that we see.
Troll is not a replacement for I disagree.
The dumb astronomers are looking in the outer space for it. No wonder they can't find it. All the dark matter in the solar system has coalesced into the form of Dick Cheney.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
We have so much evidence about the existence of the dark matter that's not even funny: https://en.wikipedia.org/wiki/Dark_matter#Observational_evidence
All indirect evidence. Personally the idea of an invisible, intangible, ethereal magical material that helps peoples sums add up is dubious at best. There are plenty of other good theories out there that do not include this populistic hypothesis.
such as http://www.springerlink.com/content/g332701735121773/
...they never asked me!
Dark Reflection
No, it does not exist. All of these effects that are attributed to dark matter are all actually due to the fact that gravity does not actually travel at the speed of light. In fact, gravity slows down as it travels. This is why there appears to be more gravity at the edges of galaxies, and even at the edges of galaxy clusters. I also explains why we have such expansive gaps between galaxy clusters.
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Dark matter is the name of the problem, not the solution.
It may not be particles, but the universe is very well described by the cold dark matter particle model (plus dark energy).
NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
that helps peoples sums add up is dubious at best.
I think it's a bit more than just coming up with stuff willy nilly.
We have these theories that work great for a lot of observations. They break down a bit for some observations, but can be "fixed" by adding dark matter. This either means the theories are wrong somehow, or there is something out there that's not been accurately observed, or maybe both. The key is to come up with experiments that can falsify the proposition that there is dark matter and that it's the cause of the aberrations.
A nice analogy is the discovery of Neptune. The theories predicted the planets would move in such a way. However they didn't quite do that. But by assuming another planet (which had not been observed), they could get their sums to add up. The testable part of it was when they said, "look here, and you should find a planet that's causing these deviations", and behold, they did.
The thing is, the current theories, even if they're wrong with dark matter, they're "close" to whatever the real situation is because they work so well in most cases. That means the "correct' theory won't be too extremely different, or must at least reduce to the current theories for the special cases we have observed.
If there are competing but "good" theories out there, the key is to find out what differentiates them in their predictions, then to devise experiments to observe what happens in those cases. If you can't devise and carry out such experiments, then it's all mere speculation.
I like to think I have an open mind when it comes to cosmology, but I've never liked the Dark Matter "theory". If they ever find direct evidence, fine, but I will remain unconvinced until then.
My personal favourite alternative hypothesis is called Modified Newtonian Dynamics, which is based on the idea that gravity exerts a stronger pull between objects that are more or less in the same inertial frame (ie at very low relative accelerations, that "acceleration is not linearly proportional to force at small values").
http://en.wikipedia.org/wiki/MOND
Obviously, a lot of people find this blasphemy, but I don't see what is so bad with modifying the law of gravity as compared to invoking "ghost matter".
I've got a bad attitude and karma to burn. Go ahead. Mod me down.
Survey Finds No Hint of Dark Matter Near Solar System
Survey:
Earth: Anyone here composed of dark matter? ...
Pluto: Not me!
Saturn: Nay.
Mars: Nope.
> Personally the idea of an invisible, intangible, ethereal magical material
> that helps peoples sums add up is dubious at best.
Yeah, prayer never helped me with math.
Dark matter is the name of the problem, not the solution.
It may not be particles, but the universe is very well described by the cold dark matter particle model (plus dark energy).
So dark matter is a filler. Much like religion.
Dark matter is the mismatch between observation and prediction in e.g. galaxy rotation curves. It looks as if there is additional matter there that doesn't radiate. "As if" is the key word here. What it actually is, is not explained by that name.
If you had x$ at the start of the month, and now you have x/3$, and you know where x/3$ went, but not the last third, you can call that "unknown expenses". Same thing.
NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
It is disappointing that the original paper doesn't not appear to consider MOND (Modified Newtonian Dynamics) or TeVeS (a Tensor-Vector-Scalar theory of gravity, the relativistic version of MOND).
The way to think about Dark Matter is it represents a problem with physics, namely excess force in the dynamics of galactic sized and larger objects. We don't know if the problem is with quantum field theories or with general relativity. The first possibility leads to theories such as Cold Dark Matter (CDM) or Weakly Interactive Massive Particles (WIMPs); the second to something like MOND / TeVeS. As literally pretty much all we know about Dark Matter is that there is excess force, neither approach can be ruled out at present.
So, it's disappointing that they didn't consider the gravitational alternative. It's not clear from the paper whether or not MOND would survive this test. Unlike CDM or WIMP, MOND effects should be present at all places in the disk, so the real question is, are they compatible with these observations?
No.
There is an effect. This is known, Dark Matter is the name for that effect until it is solved.
The name is a place holder, not the effect. We measure and predict the effect. Something is impacting large bodies. We don't know what.
It's like hears a loud banging on your wall, You know something is there, you just don't know what until you figure out a way to look.
Religion has names for things that they can't show evidence for.
The Kruger Dunning explains most post on
Sorry, you're off base. Dark matter, whatever it is, has mass but does not interact with other matter or energy. This doesn't just mean that it doesn't give off or reflect light and radiation. It also means that it's transparent to light and radiation. Per observation, there are huge swaths of "dark matter" between us and other stars/galaxies. Yet we can see these radiation emitting bodies undistorted, so whatever is there generating the gravitational effect must be totally transparent to every form of radiation we can measure. "dark matter" was a poor choice in a name. It's not dark, and it very likely is not even matter.
" Personally the idea of an invisible, intangible, ethereal magical material"
Like gravity? or solar wind?
Did you read the letter you linked to? You dio realize that he admits his proposal doesn't explain some effects we see? right?
There is an effect. We can make predictions about the effect.
SO something is happening. Proposed changes to the gravitation theory to explain the phenomena haven't played out.
Could it be some weird aspect of large scale gravity? lensing?
Sure, but the data for those ideas hasn't played out. New data will tighten up are understanding. That's how science works
SO, calling it populist is ignorant in the extreme.
The Kruger Dunning explains most post on
In other words, gravitational lensing of light waves - which is 100% direct evidence of matter - shows a region where there is matter that is clearly non-baryonic (i.e. does not interact with the electromagnetic field, a.k.a. "dark"). This is not subject to dispute. The question of what, exactly, is dark matter - is indeed still a subject of scientific research. There are, however, a number of super-symmetric theories which posit super-partners for well known particles, the most stable of which turn out to have the exact characteristics we're noting observationally. It is important to note that these theories were not tailored to account for the dark matter, but seem to fit the observational evidence quite well so far. As with all science however, theories are subject to falsification at any times as soon as new evidence comes on the scene.
There's this problem that we think we know the number of baryons that existed in the first few nano-seconds, because of the cosmic abundance of Helium and Lithium. Black holes aren't particular about not swallowing baryons (in fact, they rather prefer to), so this causes problems. If Dark Matter is matter, it must be non-baryonic matter, or we need to redo LOTS of calculations...which is going to mean a major theoretical shift, and nobody has come up with a reasonable theory to shift to. It's much easier if it's not matter at all, but some other effect. (Maybe gravity interacts with gravitational fields at long distances?) Otherwise Dark Matter needs to be non-baryonic matter, and then you've still got Dark Energy to explain.
I think we've pushed this "anyone can grow up to be president" thing too far.
Actually, there was a recent study showing the red shift of light escaping galaxies are with in 99.9% of the expected red shift for the calculated gravity-well. This means gravity does react as expected over large distances. The problem is any other forces we don't know about.
Historically, Dark Matter meant any matter not contained in a star emitting light. It originally did not mean exotic material of any kind per se.
Now, the problem posed by Dark Matter is very real and valid. The issue is, as we get better at collecting accurate data about galaxies and better at detecting possible candidates, they all keep striking out. So, in order to match observed data, Dark Matter keeps picking up all of these exotic properties. On the one had this is progress, we are eliminating things. On the other hand, Dark Matter keeps getting stranger and stranger as we can’t yet find any way to “detect” it other than the gravitational effect.
To the best of my knowledge, Dark Matter only affect Galactic sized objects, and even then only beyond a certain size. I have been an “exotic material” skeptic for some time for a very simple reason. If that much of a Galaxy is exotic dark matter by mass, how is it possible to not be a prominent effect on local objects!
Worse yet the name is too Scifi, when the general public first hears about it they end up thinking it will be the next big thing after uranium.
People obsessing over whether dark matter is actually something like a material substance or really even a form of matter are missing the point. Dark matter is a hypothesis with explanatory power, and it very likely pointing to something that really exists. It may be many things acting together that are completely unrelated to the concepts of 'dark' and 'matter', or the current hypothesis might be a very natural explanation of what is causing the observed effects. The point is that there is a consistent theory which although not complete yet is helping us understand more about the universe.
Consider things like quarks and elections, where we talk about waves and particles. But the notions of 'wave' and 'particle' are merely metaphors we use because the human imagination fails us in trying to describe things which according to the mathematics are clearly neither waves nor particles.
So, it could be that the laws of physics are slightly off, and Dark Matter is just an illusion we "see" because of the errors in physics.
Or Dark Matter could be actual matter, and is just ... dark.
Then obviously you have never dabbled in quantum field theory, where praying away infinities is how we roll.
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