Dark Matter Is Even More of a Mystery Than Expected

schwit1 writes: Using the Hubble and Chandra space telescopes astronomers have discovered that dark matter is not only invisible to direct observation, it is invisible to itself! Quoting: "As two galactic clusters collide, the stars, gas and dark matter interact in different ways. The clouds of gas suffer drag, slow down and often stop, whereas the stars zip past one another, unless they collide — which is rare. On studying what happens to dark matter during these collisions, the researchers realized that, like stars, the colliding clouds of dark matter have little effect on one another. Thought to be spread evenly throughout each cluster, it seems logical to assume that the clouds of dark matter would have a strong interaction — much like the colliding clouds of gas as the colliding dark matter particles should come into very close proximity. But rather than creating drag, the dark matter clouds slide through one another seamlessly." The data here is on the very edge of reality, built on too many assumptions. We know that something undetected as yet is influencing the motions of galaxies, but what exactly it is remains completely unknown. These results only make the mystery more mysterious.

Comments

WIMPs

[Rei]

Isn't this what one would expect if dark matter is WIMPs?

Re:WIMPs

[ShanghaiBill]

Isn't this what one would expect if dark matter is WIMPs?

Indeed. I don't think that any of this is new. The reason dark matter was hypothesized in the first place was because of the behavior of colliding galaxies, such as the Bullet Cluster. The missing mass couldn't be stars, because it didn't emit light, it couldn't be gas or dust, because it didn't experience drag, so it must be either WIMPS or MACHOs. Further observations ruled out the MACHOs. So what is new about this observation?

Re:WIMPs

[Anonymous Coward]

https://www.youtube.com/watch?v=hgee3IGYZsU

Re:WIMPs

[TMB]

Yes.

There are actually many proposed extensions to the standard model that predict dark matter particles that would be classified as WIMPs, and there are some others where the interaction is not through the weak force but through a "hidden sector" force. Some of the possible parameter space of some those hidden sector models predict a cross-section that they would have been able to detect in this experiment. So this is indeed a useful result -- it does rule out some possibilities. But they're not necessarily the possibilities that most people would be betting on anyway, so the headline is overhyped.

[TMB]

Re:WIMPs

[Rei]

That the thing about dark matter... it has a perfectly reasonable explanation (WIMPs). It's not that weird of a "thing".

Dark energy on the other hand, that's just WEIRD ;) It doesn't act like any "energy" as we know it, even though everything is clearly moving into a higher energy state. A question I've had for a while... if space itself is being inflated (or any sort of mathematically equivalent scenario) - everything inflating in all directions at all scales - wouldn't there be some sort of weak radiation signal from electrons expanding into a higher energy state due to dark energy and then collapsing back down? But I have trouble picturing how to reconcile an absolute, varying distance at the atomic scale with quantization of energy states, positions, etc...

Re:WIMPs

[dryeo]

From what I understand, currently dark energy is too weak to have local effects, with local being as large as our local cluster of galaxies.
Some do postulate that it will (continue to) increase to the point it will overcome all forces ripping even atoms apart.

Re:WIMPs

[lgw]

Dark energy is just the latest name for the Cosmological Constant - I guess it's a better name if it's not actually constant, but the cosmologists I've seen talking about it don't like the new name either (not that anyone has a better suggestion, really). The key thing about it is that the energy density of it is insanely low - I suspect that on the quantum scale it actually "rounds to 0" the way things can in QM, where no measurement is possible at that scale. I think even at the scale of our galaxy it's a very tiny effect. It's a testament to how sparse matter really is in the universe that dark matter is the dominant effect overall.

Re:WIMPs

[Bite The Pillow]

You didn't like the Wikipedia article for WIMPs. But since you put the other two as Wikipedia articles, I assume you consider it a valid source.

However, recent null results from direct detection experiments including LUX and SuperCDMS, along with the failure to produce evidence of supersymmetry in the Large Hadron Collider (LHC) experiment[2][3] has cast doubt on the simplest WIMP hypothesis.[4]

The answer isn't just "WIMPs", but a special kind of WIMP, or not one at all.

What's new?

The results, published in the journal Science on 27 March 2015, show that dark matter interacts with itself even less than previously thought, and narrows down the options for what this mysterious substance might be.

I don't have the article in the mail yet, but I'm guessing that's new. At the very least, Weakly Interacting is now Really Weakly Interacting.

Re:WIMPs

[Jane Q. Public]

Isn't this what one would expect if dark matter is WIMPs?

No... you're thinking of Dork Matter.

Just kidding. But that was a great "straight line".

Re:WIMPs

[Anonymous Coward]

Rei's right. That's exactly what one would expect if dark matter is WIMPs.

Re:WIMPs

[Jane Q. Public]

Rei's right. That's exactly what one would expect if dark matter is WIMPs.

I know. You got the "that was just a joke" part, yes?

Re:WIMPs

[foreverdisillusioned]

Dark energy is just the latest name for the Cosmological Constant

You know, I'm as happy as anyone else that physicists have been able to do so much with their models, but what kind of navel-gazing mathurbation is this?

Dark energy is an observed physical phenomenon.

The cosmological constant is a term in an equation. It's a very good equation, mind you, but a lot of very good equations have later turned out to be wrong or good for only a special class of phenomena. Equations can predict, but they don't prove anything. It's also worth noting that the cosmological constant was supposed to predict a force that would hold the universe together. Dark energy is a force that is tearing the universe apart. Someone clever pointed out that hey, that works if you just flip the sign of the cosmological constant but I'm not sure I'd call that a win.

And regardless, I don't think it's reasonable to imply that the territory is imitating the map.

Re:WIMPs

[Altrag]

what kind of navel-gazing mathurbation is this?

Its the kind of mathurbation that happens when someone looks at the "dark energy" in real data.. tries to match it with the equations.. and discovers that it exactly fits what Einstein's cosmological constant would have done if he hadn't rejected the idea at the start.

The reason there are two different names is because it came from two different sources (one data, one math). A bit of a "holy shit even Einstein didn't realize how smart Einstein was" moment. The second paragraph of the Wikipedia article (somewhat vaguely) outlines that connection.

That said, since we know so little about dark energy beyond the fact that it exists, its possible that its just a coincidence for it to match the cosmological constant. So technically its not entirely accurate to say the two concepts are the same.. but pending further discoveries on the nature of dark energy, they may as well be considered the same (in terms of GR at least.. no idea how dark energy works in M-theory or MOND or whatever other theories that aren't directly based on GR equations.)

Re:WIMPs

[ultranova]

That the thing about dark matter... it has a perfectly reasonable explanation (WIMPs). It's not that weird of a "thing".

I dunno. Usually when a theory requires more and more unseen entities over time it's a sign that it's time to replace the theory. We know General Relativity is incomplete, both because it doesn't take into account quantum effects and because it has internal contradictions - specifically, it assumes a continuous spacetime geometry but predicts non-continuous points (black hole singularities). Most likely Einstein simply missed some observer-specific assumption - for example, GR assumes mass-energy has an exact distribution rather than probabilistic one - and thus GR is not completely general.

A question I've had for a while... if space itself is being inflated (or any sort of mathematically equivalent scenario) - everything inflating in all directions at all scales - wouldn't there be some sort of weak radiation signal from electrons expanding into a higher energy state due to dark energy and then collapsing back down?

No, because a continuous force wouldn't drag electrons up and then let them drop back down. What it would do is alter orbital structure and energy levels. But how they'd be altered depends on how quantum mechanics and GR combine, which we don't currently know.

Re:WIMPs

[Rei]

Could you elaborate on what you mean by "alter orbital structure and energy levels"? Are you saying that the energy level of, say, ground state would increase with time? If so that sounds... weird. And sounds like *that* should have detectable consequences too, if so.

Re:WIMPs

[Rei]

One thing that dark energy can't be is *all* fundamental constants, plus position, velocity, etc scaling up evenly. Because if such was the case then there would be no perceptible change.

If youe saying that for example what is ground state would change too then it seems like you're arguing that things at the quantum level *aren't* moving into higher energy states. But things at the macroscopic level absolutely are moving into a higher energy state. So are you arguing that dark energy doesn't act on the quantum scale? I find that difficult to accept if so.

Re:WIMPs

[foreverdisillusioned]

I need to figure out what all of that subscript means and meditate on it sometime. To me, "constant" is just some fiddly fucking detail utterly lacking in profoundness. Like the thing you forget to tack on at the end of an indefinite integration. But that one doesn't look easily separable. So... hm.

My gut still says that if the constant was predicted to be a negative value and turned out to be a specific positive value, that is in no way a slam-dunk. I've also heard some talk about it not remaining constant at all.

Einstein deserves every bit of his reputation, but the armchair physicist in me still says the most likely explanation is going to be a total overhaul that pushes his equations firmly into 'wrong' territory (or rather, 'right' for only certain non-generalized circumstances). We have a bunch of messed-up things going on with gravity here: dark matter, dark energy, a lack of quantum gravity / GUT, contradictory theories about what happens with singularities (black holes, big bang), still no confirmation of gravitational waves, no clear refutation or explanation of time travel / closed time-like curves, curious galactic rotational anomalies (supposedly explained by dark matter, but I'm unconvinced), no experimental confirmation that antimatter has exhibits/exerts gravitational pull in the same way as normal matter, etc. Very easy (or at least very tempting) to imagine the next daydreaming Swiss patent clerk suddenly coming up with something that wraps up all of these issues in a tidy package.

Re:WIMPs

[buchner.johannes]

That the thing about dark matter... it has a perfectly reasonable explanation (WIMPs). It's not that weird of a "thing".

Having one solution does not suffice, you need to prove it. WIMPs have been proposed, but they require Supersymmetry (which is not proven), and also WIMPs have never been detected in particle accelerators. Dark matter is a weird thing, because one way or another, you need new physics which does not interact using the strong force or electromagnetism, is present already in the very early Universe (380000 years after the Big Bang).

Re:WIMPs

[Anonymous Coward]

Someone clever pointed out that hey, that works if you just flip the sign of the cosmological constant but I'm not sure I'd call that a win.

That is the only kind of win there is in science. Either a theory matches observation or it doesn't. There is the possibility of arguing which of two explanations matches observations with fewer assumptions, etc., but that can be kind of rare by the point observations have been found to break older theories and more often than not only one newer theory does a decent job of matching observations.

Re:WIMPs

[Anonymous Coward]

WIMPs have been proposed, but they require Supersymmetry (which is not proven),

They do not require supersymmetry, as there is a long list of alternatives proposed, and the possibility that none of the proposed explanations for WIMPs are the correct one despite WIMPs being the possible correct explanation for dark matter. The properties required of dark matter are so simple, that there is no shortage of possible ideas for generating materials with said properties.

Re:WIMPs

[Bengie]

still no confirmation of gravitational waves

This is a peculiar one. While we have not directly detected gravitational waves, when watching a binary neutron star, the orbits degrade exactly as predicted if gravitational waves exist. No other known theory would give this exact effect.

Re:WIMPs

[Anonymous Coward]

"No other known theory would give this exact effect."

Well, there's your problem.

Re:WIMPs

[lgw]

Equations can predict, but they don't prove anything.

You've got that backwards, I'm afraid. Science isn't in the business of proof; proof is the realm of mathematics and formal logic. One can prove that one equation, or other statement in a formal language, is equivalent to another under some axioms. Once cannot prove anything about the universe we inhabit.

Science is in the business of useful, predictive models. Dark matter and energy are both "dark" in the sense that we don't have one of those yet. We can characterize them, and there's been some real progress in dark matter as WIMP models predicted the CMBR data nicely, but still, there's so little data to go on. There's a forest of hypotheses for each, and not much yet to weed them out.

If the cosmological constant is, in fact, constant, then it's remarkably close to "0", which is bothersome as it requires such "fine tuning", which is another way of saying we're missing something big. Inflation models also deal with the expansion of space, but don't seem to solve the dark energy problem in any natural way. And QM also has a similar concept: in what been called the "worst prediction ever", the value predicted from QM is wrong by 120 orders of magnitude - so no help there.

Re:WIMPs

[foreverdisillusioned]

You've got that backwards, I'm afraid. Science isn't in the business of proof; proof is the realm of mathematics and formal logic.

Except there are a vast number of physics equations describing universes that do not exist--Higgs-less models, for example, can probably be tossed in the trash at this point. They are mathematically sound. There is no formal logical flaw with them. But they do not match reality.

Math proofs are meaningless without physical observations to back them up.

Re:WIMPs

[mbone]

No. This really applies _to_ WIMPs. It doesn't apply to condensed dark matter, or to axions.

Re:WIMPs

[mbone]

That's exactly backwards.

The WIMP miracle is over; unless the LHC finds success with its Hail Mary pass, interest in WMPs will inevitably decline, and people will look (are looking) at other explanations for Dark Matter.

Dark Energy, on the other hand, is just a cosmological constant. Nothing mysterious (from a General Relativistic standpoint) about it at all.

Re:WIMPs

[Anonymous Coward]

While there were a few theories that suggested a WIMP particle might be observable with LHC, there is no shortage of ideas that would not be observable with the LHC. The LHC does little to eliminate a large number of WIMP candidates.

Re:WIMPs

[mbone]

Dark energy is just the latest name for the Cosmological Constant

You know, I'm as happy as anyone else that physicists have been able to do so much with their models, but what kind of navel-gazing mathurbation is this?

Dark energy is an observed physical phenomenon.

The cosmological constant is a term in an equation. It's a very good equation, mind you, but a lot of very good equations have later turned out to be wrong or good for only a special class of phenomena. Equations can predict, but they don't prove anything. It's also worth noting that the cosmological constant was supposed to predict a force that would hold the universe together. Dark energy is a force that is tearing the universe apart. Someone clever pointed out that hey, that works if you just flip the sign of the cosmological constant but I'm not sure I'd call that a win.
 

This is physics. Everything is a term in an equation.

The cosmological constant is the only free parameter in Einstein's equations. The. Only. One. And, it fits exactly all of the available data. Unless and until that changes, there is no good reason to believe to believe that we do not live in a de Sitter space.

Re:WIMPs

[mbone]

Yeah, but that is widely considered not to be good enough.

Re:WIMPs

[mbone]

That the thing about dark matter... it has a perfectly reasonable explanation (WIMPs). It's not that weird of a "thing".

I dunno. Usually when a theory requires more and more unseen entities over time it's a sign that it's time to replace the theory. We know General Relativity is incomplete, both because it doesn't take into account quantum effects and because it has internal contradictions - specifically, it assumes a continuous spacetime geometry but predicts non-continuous points (black hole singularities).

That is not thought to be an internal contradiction of General Relativity, as, even though GR does have singularities, thanks to event horizons and cosmological censorship, there are no known cases where you can use these singularities to derive multiple different estimates of the same observational quantity (which is what having an inconsistent physical model means). I don't believe that there are any mathematical proofs of this, but I suspect you would have to come up with a counter-example if you wanted to convince people GR was self-contradictary.

Re:WIMPs

[mbone]

Math proofs are meaningless without physical observations to back them up.

Fully agree. And, as it happens, General Relativity has a massive amount of physical observation backing it up, and no physical observations contradicting* it.

* If you believe in MOND / TeVeS, then the dark matter observations contradict GR. Let's just say that there is not yet consensus around that view.

Re:WIMPs

[mbone]

I don't have the article in the mail yet, but I'm guessing that's new. At the very least, Weakly Interacting is now Really Weakly Interacting.

Here you go.

From my perspective, it hardly changes a thing (it lowers the cross section / mass constraint a little, but not even an order of magnitude). But, then, I'm not a WIMP guy.

Re:WIMPs

[foreverdisillusioned]

Unless and until that changes, there is no good reason to believe to believe that we do not live in a de Sitter space.

Unless and until we have quantum gravity and a whole slew of gravity-related mysteries are conclusively resolved (dark matter, weird galactic rotational speed synchronization, dark energy overwhelming gravitational attraction, etc), there is no good reason to believe Einstein's equations are complete.

Re:WIMPs

[foreverdisillusioned]

It depends what you mean by "contradiction". If you look at a list of lingering questions in physics, a lot of them have to do with gravity: quantum gravity is the last remaining force needed for a GUT, the causal mechanics of closed timelike curves, the physics of singularities, the gravitational pull of antimatter (we assume it works like regular matter, but does it? If it had repulsive gravity, that would be interesting), no solid proof of gravitational waves, bizarre galactic rotational speeds, etc.

Newton's equations are strictly speaking "wrong" for predicting orbital mechanics. But they are good enough in most cases. Given the outstanding mysteries, I think it's very possible that we'll discover that Einstein's equations are even more "good enough", yet still incomplete.

Re:WIMPs

[mbone]

Well, sure. I have tested General Relativity, and would love to have found a case where it was not "good enough." But, that is different from an internal contradiction, which as far as we know GR doesn't have.

Re:WIMPs

[lgw]

Yes, you've got the core of the scientific method right in hand. You use math to formalize some model that explains both old and new observations, then you extrapolate using the math to make predictions, then you weed out all the failures with the next set of data. Everyone in physics does understand this, except maybe the string theorists, who went off the rails some time ago and IMO are an embarrassment to the field now.

But the math is the tool that lets you make that prediction, and it's not enough for the current model to be "wrong", you have to have an alternative that successfully predicts new data. That what all the internet cranks and crackpots seem to miss: yes, fine, you can contrive limitless alternative explanations for the existing data. So what? It's all about the predictions, and those are usually meaningless without the math to back them up, to set bounds and make them falsifiable.

The inability of GR to give a good model at universe-scale is hardly new - Einstein himself identified the need for a cosmological constant quite early on. The mystery has only deepened since - but that doesn't necessarily mean anything's wrong with GR, only that there's more to learn (dark energy is easy to describe in GR terms, but GR gives no explanation of why it's there in the first place).

Re:WIMPs

[foreverdisillusioned]

Well correct me if I'm wrong, but GR primarily aims to explain the laws and effects of gravity. It does this rather well in our solar system. But for the reasons I've outlined, it fails on several counts to predict the movement at larger distances (on the scale of galaxies.) You could claim "well, that's just another hidden force at work--GR is flawless!" And that might indeed be true. But I don't think it's absolutely, self-evidently true.

Re:WIMPs

[Altrag]

Well the "constant" that Einstein defined was never really given a value. It was shown fairly early that "if" it had certain ranges of values, we would be able to observe certain effects. Einstein for whatever reason decided that his constant was a mistake ("his biggest blunder" according to him) and that it should always be zero.

Newer observations ended up showing that rather than being a blunder, a non-zero constant ended up being the simplest way to explain the accelerating expansion of the universe, which pretty much nobody expected to even be a possibility prior to finding out that yep, its actually the way things are.

All that said, its no secret that GR and/or QM (or more likely both) are just limits of some deeper theory as you noted. Whether that ends up being M-theory or something completely different is up for grabs (and it could be generations before we can build accelerators large enough to probe those energy levels.)

But a really good approximation is still very useful (hell we still use Newtonian mechanics for the most part in the real world.. pretty much only theoretical physicists, spacecraft/satellite designers and computer engineers really care about the high energy / high speed / small size scales where Newton breaks down (well I'm sure there's other fields that I'm not thinking of but the number of them is comparatively small.)

Re:WIMPs

[Altrag]

Not especially peculiar. Gravity is a tiny tiny effect compared to the other forces, which equates to being extremely hard to detect (and remember its not just a question of "is there gravity" which is an obvious yes -- the Earth is pulling us in, the Sun is pulling us in, etc.. so you can't just detect gravity you have to be able to separate out the gravity that you're looking for from all of the other gravitational effects in the area.)

We had no confirmation of the top quark until we built an accelerator large enough to confirm it.. we had no confirmation of the Higgs boson until we built an accelerator large enough to confirm it.

And we'll have no confirmation of gravity waves until we can build a device large enough to confirm it (which will likely be a massive interferometer rather than accelerator.. but when I say massive I mean that some of the suggestions are along the lines of "a few million km".)

"Haven't seen it yet" is not the same as "it doesn't exist."

Re:WIMPs

[TechnoJoe]

Dark energy is an observed physical phenomenon.

Just because it's observed, doesn't mean it's real. See Heliocentrism and epicycles.

The idea of Dark Matter was invented when astronomers observed objects on the outer edges of galaxies traveling too fast relative to objects in the center. However, this could also be explained by variances in the passage of time. In the center of the galaxy where mass is greater, time would pass more slowly relative to the outer edges. No magic, invisible Dark Matter required.

Dark Energy was invented when astronomers observed that the "expansion of the universe" was accelerating. However, this could also be explained by a natural shift in light as it travels over distances through time.

Gavin Wince details these alternatives in The Dark Side of Time. It always urks me when scientists assume a model is true because it happens to fit the facts. There may be multiple, different explanations that all fit those same facts. Science is about proving, not assuming or making stuff up. I'm not saying Gavin Wince is right, but we need to keep our minds open to new ideas. Otherwise, we would still be on Newton's gravity instead of Einstein's relativity.

P.S. I put "expansion of the universe" in quotes because that might be another example of jumping to conclusions too. See: Did the Big Bang ever happen? Quantum model predicts universe has NO beginning - and it could even explain dark energy

Re:WIMPs

[Anonymous Coward]

However, this could also be explained by variances in the passage of time.

If you are talking about variations in the passage of time due to special and general relativity, then the effects at the center of the galaxy are many orders of magnitude too small to matter. If you are talking about some other effect, then you would need to explain why it hasn't affected detailed spectroscopic measurements, and account for why some galaxies lack this effect, and yet not end up with a larger pile of arbitrariness than more mainstream theories.

And you should find better sources than short newspaper blurbs if you care about such things, or learn to read such things very carefully, because the idea discussed in your final link doesn't contradict or reject the expansion of the universe at all and in fact explicitly involves the expansion of the universe.

Re: WIMPs

[Anonymous Coward]

"And we'll have no confirmation of gravity waves until we can build a device large enough"

or far enough away from large objects. Like a Hubble telescope, but for gravity, maybe out in the interstellar zone.

Re:WIMPs

[ultranova]

Could you elaborate on what you mean by "alter orbital structure and energy levels"?

I mean part of the electrostatic attraction between atomic nucleus and orbiting electrons should be countered by expansion of space between them, which in turn affects stable electron orbits. In fact all forces should get weaker with distance faster in an expanding space than in flat space.

Electromagnetic force is mediated by virtual photons, who's wavelength gets longer as space expands, thus sapping electromagnetism of some of its native strength and somewhat altering the lowest-energy point of all structures held together by it.

Re: WIMPs

[Anonymous Coward]

or far enough away from large objects. Like a Hubble telescope, but for gravity, maybe out in the interstellar zone.

Gravity waves don't work that way...

Re:WIMPs

[Rei]

In fact all forces should get weaker with distance faster in an expanding space than in flat space.

That seems like quite an assumption on your part, if I'm understanding you correctly. We can't just assume that all properties of spacetime are scaling evenly - if they did, then we'd perceive no effect at all.

But perhaps I'm misunderstanding you.

Re:WIMPs

[Anonymous Coward]

But the math is the tool that lets you make that prediction, and it's not enough for the current model to be "wrong", you have to have an alternative that successfully predicts new data. That what all the internet cranks and crackpots seem to miss: yes, fine, you can contrive limitless alternative explanations for the existing data. So what? It's all about the predictions, and those are usually meaningless without the math to back them up, to set bounds and make them falsifiable.

What do you think of, and recommend for, fields such as medical research? Personally I've come to the conclusion that we will simply need to develop the theories in terms of math to move forward and that most of the claims have not really been compared to reality. Just convincing others that your explanation "makes sense" is not sufficient, yet that is what they rely upon. I wish more physicists would weigh in on this problem.

Re:WIMPs

[Anonymous Coward]

More than half of the people I've seen employed as "biophysicists" are not applying physics principles to biology, but instead just hired to help give some mathematical oomph to a research project. In a lot of cases the math comes down to network analysis and computational numeric. There are plenty of biologists that can run circles around physicists with proper statistics, but not enough.

Re:WIMPs

[Anonymous Coward]

You are correct to note that "vagrant" equations are not really what is desired. Am I correct that you are saying the missing aspect is the first principles and deductions rather than the math skills?

Re:WIMPs

[foreverdisillusioned]

As I mentioned elsewhere in this thread, a key thing to realize is that many internally consistent and mathematically correct models have been built in physics, only to be discarded because they don't match reality. There are an infinite number of universes that don't exist, but math lets us describe then perfectly.

Einstein himself identified the need for a cosmological constant quite early on.

But he quickly realized that this "need" (as it was originally conceived) was entirely psychological/emotional in nature--the effect it was supposed to explain didn't exist and so the term became useless. Einstein himself called it a mistake.

Some people are now disagreeing and saying that he was so brilliant that he solved a problem no one knew existed, but I am highly skeptical of this sort of freewheeling approach. Even if the Cosmological Constant can be made to worth mathematically to describe Dark Energy, you're on very shaky ground trying to re-purpose it to describe a totally different phenomenon from the thing Einstein was originally envisioning when he created that term.

Tying together the above two points results in the key thesis I was dancing around in my original post: "Explaining" an unexpected observation by shoehorning it into a term in an existing equation--taking a superfluous term and making it important again by flipping the sign and allowing it to refer to a different phenomenon--is a very weak and queasy "win". This kind of re-purposing strikes me as a very shady way of recycling a bit of trash that should have been tossed out many decades ago. Let me put it another way: the cosmological constant term should have never been in there to begin with. These aren't my words; they are (more or less) Einstein's words. If Hubble had made his discoveries sooner, Einstein would not have put the constant in there. So, in a universe where the cosmological constant term doesn't exist, what do we do when we see dark energy? Do we create the cosmological constant exactly as it is now? Would it make intuitive sense to create that term out of whole cloth and add it to alternate-universe Einstein's equations?

Anyhow, it's as you've said: GR has serious unresolved issues at universal scales, but also at galactic scales (rotational issues, Dark Matter.) Additionally, it has issues at the QM level, which makes it the primary thing standing in the way of a GUT. Just consider for a moment how gravity stands alone, unconnected to the rest of physics... and it has significant mysteries (dark energy, dark matter, galactic rotational behavior, closed timelike curves, singularities), and it also has important questions that we think we already know the answer to but we haven't verified (gravity waves, gravitational behavior of antimatter and other uncommonly seen particles, the existence and properties of negative mass / negative energy)

Conclusion via Occam's razor: GR is wrong. Not toss-it-in-the-garbage wrong, but wrong in the way that Newton's equations predicting the orbit of Mercury were wrong.

Re:WIMPs

[Anonymous Coward]

Nah, you're wrong there. Problem is, science is ignorant to anything suggesting they've been wrong all these years, and the fundamentals need to change.
That fundamental is the assertion that gravity alone forms the universe we see and love. So when you immediately discount other factors, you're forced to explain observed phenomena it terms of gravity. As we don't see what's causing the gravity (based on matter) then we come to the conclusion that there's dark matter. Then when we see objects accelerate where we find no cause, we invent dark energy.

In reality, these phenomena are much easier explained as an electrical phenomena, when we look at the universe and see plasma making up the vast majority of matter in the universe, and where there's plasma, there's electric currents, and where there's electric currents, there's magnetism. You know, trillions of times more powerful than gravity.

No need for exotic matter that doesn't exist, just some sound reasoning, and decent science.

Re:WIMPs

[lgw]

As I mentioned elsewhere in this thread, a key thing to realize is that many internally consistent and mathematically correct models have been built in physics, only to be discarded because they don't match reality. There are an infinite number of universes that don't exist, but math lets us describe then perfectly.

Yes, everyone in science realizes this, believe it or not (though I'll grumble about string theorists). What else do you think the scientific method is?

But he quickly realized that this "need" (as it was originally conceived) was entirely psychological/emotional in nature

I believe you've got that backwards., IIRC. GR was first published in 1915. Hubble discovered in 1929 that the universe was expanding, which GR didn't explain in any way (not it it contradict). Einstein tried a couple of approaches to reconcile the new data with GR, one of which along the way was the cosmological constant. Thus far, that still seems to b the bats model (and it has nothing to do with GR).

"Explaining" an unexpected observation by shoehorning it into a term in an existing equation--taking a superfluous term and making it important again by flipping the sign and allowing it to refer to a different phenomenon--is a very weak and queasy "win"

Sure - that's science. There's always an establishment trying to explain away new data, and many trying to make a name for themselves by overturning everything with their great new theory. Sometimes the same guy doing both. But GR doesn't come into conflict with dark energy theories, any more than it does with fluid dynamics or genetics - it just doesn't explain those things.

Anyhow, it's as you've said: GR has serious unresolved issues at universal scales, but also at galactic scales (rotational issues, Dark Matter.) Additionally, it has issues at the QM level, which makes it the primary thing standing in the way of a GUT.

No, it really doesn't. There's no conflict at all between GR and dark matter, and in fact GR gives us one of the 3 sets of evidence for dark matter in the first place: gravitational lensing consistent with a large mass that we can't see. As far as QM, there's certainly more to learn, and I'd bet GR becomes a poor model at sufficiently small scale, as it assumes spacetime is smooth.

Conclusion via Occam's razor: GR is wrong. Not toss-it-in-the-garbage wrong, but wrong in the way that Newton's equations predicting the orbit of Mercury were wrong.

GR has so far successfully accurately predicted more far-fetched and surprising results than just about anything else in physics. It's the most well-tested of physical theories. There may well be a scale or conditions in which it fails, but skepticism of such claims is well justified.

Re:WIMPs

[Anonymous Coward]

You know, trillions of times more powerful than gravity

This seems to be a common fallacy, as there is no single number that represents how much stronger one is than the other, and it depends heavily on the situation and basic things that can be measured, even in deep space (e.g. electric and magnetic fields from spectroscopy, and directly from space probes). Otherwise, at face value you're arguing that we would never notice gravity in day to day life.

That fundamental is the assertion that gravity alone forms the universe we see and love.

Not based on any mainstream astrophysics conference, journals, and even textbooks, which spend quite a lot of time talking about impact of plasma physics, and have done so for decades.

Re:WIMPs

[RockDoctor]

The reason dark matter was hypothesized in the first place was because of the behavior of colliding galaxies,

Not by a large part of a century. (Expressing it as a fraction of a century to get the magnitude of the difference across. I feel a bit wobbly and I'm not yet a half century old.)

In the late 1930s and early 1940s, while some palaver called world war two was happening in some parts of the world, astronomers were mapping the rotational velocity profile of rotating galaxies. to their surprise they found that the velocity profile did not match the distribution of luminous matter (stars), but had to incorporate a significant quantity of non-luminous ("dark") matter in addition to the luminous matter. And thus was born the mystery of the dark matter. Constraints on the properties of the dark matter have tightened, slowly, over the decades, and estimates of it's quantity have increased (at first) then stabilised at around 4 times the gravitating mass of the luminous matter (note : I'm not tying it's gravitating and inertial mass to each other - we don't know anything where the two aren't exactly equal to depressing precision, but I'm not aware of any good reasons why that is the case).

It's not a new problem. It's a much older problem than our ability to clearly image colliding galaxies.

Non-linear gravity

[Anonymous Coward]

We're trying to explain inflation and the motions of stars orbiting galaxies not matching our naive model.... couldn't a non-linear gravity model explain all this without the dark energy/matter hocus pocus?

Re: Non-linear gravity

[Anonymous Coward]

They acting like there isn't anything at all. I wonder what would cause that? Hmmmm... Nothing as far as I know.

Re:Non-linear gravity

[painandgreed]

We're trying to explain inflation and the motions of stars orbiting galaxies not matching our naive model.... couldn't a non-linear gravity model explain all this without the dark energy/matter hocus pocus?

Sure, but that would involve even greater hocus pocus than the current theory and fails at explaining other observations. So far, trying to come up with any hypothetical explanation involving MOND has been so complex that nobody has been able to come up with one that explains even the rotation of galaxies. If you or any other person could come up with a good law of nonlinear gravity that works, even if it completely fails at any of the other observations, there's a paper in a prestigious journal and some physics cred for you.

Re:Non-linear gravity

[Anonymous Coward]

So far, trying to come up with any hypothetical explanation involving MOND has been so complex that nobody has been able to come up with one that explains even the rotation of galaxies

Do you have a source for this? Which galaxies is MOND unable to fit?

Re:Non-linear gravity

[Bengie]

We know about Dark Energy because objects are moving away from us faster than light. Since it is impossible for something to move through space faster than c, then more space must be getting created. If space is being created, and objects are receding away from us at a known rate, then we can calculate the amount of energy required.

A change to gravity does not work because we have already measured the gravity at these ranges to be within 99.9% of the expected values. Advancements in optics and sensors has allowed us to measure minute changes in red shifts and detect curved paths that light takes. Mix all of this together and you can measure gravity quite accurately. It's working as expected. Even worse, we're able to see the gravity but unable to see the matter causing it.

Re:Non-linear gravity

[pz]

We're trying to explain inflation and the motions of stars orbiting galaxies not matching our naive model.... couldn't a non-linear gravity model explain all this without the dark energy/matter hocus pocus?

Gravity is non-linear, or maybe you didn't notice that distance is in the denominator? It's linear in mass but really very non-linear in distance. m1*m2/r^2. Not even remotely linear.

To review: double m1, you get double the force: linear in m1. Double m2, you get double the force: linear in m2. Double r and, WHOA NELLIE you get 1/4 the force: massively (pun intended) non-linear!

Re:Non-linear gravity

[Anonymous Coward]

here is the deepest secret nobody knows
(here is the root of the root and the bud of the bud
and the sky of the sky of a tree called life;which grows
higher than soul can hope or mind can hide)
and this is the wonder that's keeping the stars apart

-- cummings

Re:Non-linear gravity

[Anonymous Coward]

We know about Dark Energy because objects are moving away from us faster than light.

Well, there's Suntola's Dynamic Universe theory which doesn't require Dark Energy - it explains redshift observations of distant galaxies by using Variable Light Speed (i.e. c has been smaller in the past).

Re:Non-linear gravity

[Anonymous Coward]

https://youtu.be/SwyTaSt0XxE?t=25m10s

Seems like a pretty good talk, but not sure how much of this still holds as this isn't my field.

Re:Non-linear gravity

[Anonymous Coward]

Absence of theory is not evidence of absence. LOL

Re:Non-linear gravity

[Bengie]

The Universe is 13.8bil years old and has a diameter of 91bil light years. Explain that. CBR is uniform, which requires inflation, or requires some truly absurd assumptions to make it work.

Re:Non-linear gravity

[Bengie]

That phrase can be said for everything. Yes, we understand, don't limit yourself to thinking inside the box, but don't use it like a valid argument for trying to guilt the community into further exploring ideas that seem completely incorrect. Use your own time and explore those ideas that no one cares to look into anymore. Maybe history will correct the rest of us and bathe you in the glory of "I told you so!".

Re:Non-linear gravity

[zippthorne]

What objects are moving away from us faster than light and how was this determined?

Re:Non-linear gravity

[Anonymous Coward]

That ratio is the same as the ratio of Milgrom's acceleration constant to the acceleration required to go from 0 to light speed in 13.8 billion years.

Re:Non-linear gravity

[mbone]

What objects are moving away from us faster than light and how was this determined?

None. That poster was overly enthusiastic.

Re:Non-linear gravity

[Anonymous Coward]

Perhaps there is a 2*pi somewhere that shouldn't be there?

Re:Non-linear gravity

[Anonymous Coward]

"there's a paper in a prestigious journal and some physics cred for you."
So I spend a huge amount of time learning physics and then creatively coming up with a theory and all I get is a paper published and some physics credit?
Essentially, I lose a huge amount of money and gain a little fame which I cannot easily convert into money. Even if I knew the answer I probably couldn't justify writing the paper as I need the time for other ventures more likely to result in a profit. As a capitalist, I have to be able to convert my effort into capital/cash in order to justify giving up the results of my effort. There is no market!

*WHOOP!* *WHOOP!* PC Police Takedown!

[Irate Engineer]

Ahem; that's "Matter of Color", thank you very much.

THAT expected?

[Anonymous Coward]

anyone proofreading this stuff?

Re:That expected?

[Anonymous Coward]

Maybe your browser is broken? The title shows up as "Dark Matter Is Even More of a Mystery Than Expected" for me.

Re:That expected?

[nemyax]

Apparently it had an abortion in the end.

Re:That expected?

[Paradise Pete]

Either you misread it or they changed it without noting the edit. I hope it's the former. the RSS feed also has "than", which lends a small bit of extra credence to that.

That expected?

[Anonymous Coward]

Dark Matter Is Even More of a Mystery That Expected
 
Dark matter is a mystery that expected what? Please tell us what it expected, Soulskill!

what if...

[Anonymous Coward]

physics at that scale simply isn't the same as we know it "down here"?

Re:what if...

[Anonymous Coward]

There have been several theories built on that assumption, most prominently one called MOND (MOdified Newtonian Dynamics), but more recently one that builds on relativity rather than Newtonian gravity/dynamics.

But none of these theories (hypotheses?) have gained much acceptance from the physics community, as far as I know.

Re:what if...

[Anonymous Coward]

But none of these theories (hypotheses?) have gained much acceptance from the physics community, as far as I know.

They haven't even gained much "acceptance" from their own proponents who will be the first to admit that there is still a lot of question or arbitrariness (e.g. fitted parameters) and short commings in explaining the diverse observations that dark matter can. Otherwise though, they get a lot of attention and curiosity from the physics community, as despite internet postings insisting otherwise, physicists are aware of the possibility of gravity being wrong. Just so far, despite numerous groups working on the problem, it hasn't panned out.

Re:what if...

[mbone]

There have been several theories built on that assumption, most prominently one called MOND (MOdified Newtonian Dynamics), but more recently one that builds on relativity rather than Newtonian gravity/dynamics.

But none of these theories (hypotheses?) have gained much acceptance from the physics community, as far as I know.

Yes, and one reason is that they find it hard to model these kinds of galaxy cluster observations in MOND / TeVeS without assuming there is also some dark matter or some other non-MOND effect involved. Now, that could be (and MOND proponents will point out that standard CMD also has its problems, e.g., with the core/cusp problem, and we don't throw out CDM every time such a problem is encountered), but it certainly takes some of the shine off of the theory.

Not really

[Anonymous Coward]

All the descriptions I remember assume dark matter is weakly interacting including with itself and often modeled as a form of incompressible gas so I don't understand surprise in either TFA or article. Who were the people thinking otherwise and why?

Check the Equations/Assumptions

[Anonymous Coward]

Perhaps the gravity equations break down at large distances or low accelerations. If that is the case, putting spheroid clouds of invisible matter everywhere could get the equations to work, but in the end it will need to be equivalent to the new math.

I don't think the hidden/dark matter hypothesis is ruled out at all, it has gotten pretty far. It really does sound just like epicycles though.

Re:Check the Equations/Assumptions

[Bengie]

They've already checked this years ago. Dark Matter is nearly 100 years old and still not solved. Do you really think 100 years of scientists haven't thought up of these ideas in an attempt to falsify Dark Matter?

Re:Check the Equations/Assumptions

[Anonymous Coward]

Do you really think 100 years of scientists haven't thought up of these ideas in an attempt to falsify Dark Matter?

I do not think that specific thing you wrote. However:

Why did you decide to reconsider Newton's second law?

It wasn't that I was struck by a conviction that there must be something wrong with DM. I just thought it would be legitimate and interesting to explore this possibility. I tinkered with modifying the distance dependence of gravity, and also with the idea of adding a new 1/r2 force that couples not to mass, like gravity, and not to charge, like electricity, but to angular momentum. These attempts didn't go very far. Toward the end of a sabbatical year, in May 1981, I hit upon the idea of departing from standard dynamics at low accelerations.

http://www.americanscientist.org/issues/pub/dark%E2%80%90matter%E2%80%90heretic

The blogger (@StartsWithABang) contacted @scilogscom on January 24 by replying to a 15-day old tweet that announced our blog's move to the new domain. He tweeted “Bummed that @scilogscom is in the business of promoting contrarian scientist viewpoints.”, and asks the SciLogs.com community manager (@notscientific) “[Why] are you allowing @scilogscom to promote contrarian voices that undermine public understanding of [science]?”, adding “You have taken on "Dark Matter Crisis" blog, whose mission is to undermine all of physical cosmology & promote MOND.”

http://www.scilogs.com/the-dark-matter-crisis/2013/03/08/the-dark-matter-crisis-continues-on-the-difficulties-of-communicating-controversial-science/

Supersymmetry ?

[cyberspittle]

If there is a vacuum in space, would their need to be a corresponding antivacuum?

Re:Supersymmetry ?

[ShanghaiBill]

If there is a vacuum in space, would their need to be a corresponding antivacuum?

No. Because of Heisenberg's uncertainty principle, there can never be a complete vacuum. Even if there was, you couldn't measure it without destroying it.
 

Re:Supersymmetry ?

[Anonymous Coward]

I need a better idea of your thinking, before I can comment on how dumb your question is.

Re:Supersymmetry ?

[PolygamousRanchKid]

If there is a vacuum in space, would their need to be a corresponding antivacuum?

There is an antivacuum in the universe . . . more specifically, in my apartment.

At least that is what my cleaning girl claims . . . when she tries to vacuum here . . .

Re:Supersymmetry ?

[TechyImmigrant]

If there is a vacuum in space, would their need to be a corresponding antivacuum?

There is an antivacuum in the universe . . . more specifically, in my apartment.

At least that is what my cleaning girl claims . . . when she tries to vacuum here . . .

An antivacuum is usually called 'gas'.

Re:Supersymmetry ?

[Livius]

Leaf blower... ...in space!

Re:Supersymmetry ?

[Nemyst]

I'm guessing the GP also farts a lot then.

Re:Supersymmetry ?

[dryeo]

More likely "plasma" which is much more common then "gas"

Re:Supersymmetry ?

[TechyImmigrant]

Right, but plasmas are a bit thin on the ground where humans live and humans are the ones who call things things. There may be aliens who call plasmas and gasses things, but they probably have different words for them. "No Fnakquar, an antivacuum is called a 'congressman' " or some such.

Electric Universe

[Jaborandy]

The answer to what they're missing: Electric charge and currents.

The electric universe folks explain that galactic rotation rates do not require dark matter to make sense. The electric current through the galaxy adds forces on the charged stars and gasses that adds up to explain the observed motions. This article sheds more light on the problems with the dark matter theories. It's time to more strongly consider the possibility that dark matter isn't the answer.

--Jaborandy

Re:Electric Universe

[Anonymous Coward]

The electric universe folks explain that galactic rotation rates do not require dark matter to make sense.

I have heard this but never seen the equations they are using and the rotation curves they predict compared to data. Got a link?

Re:Electric Universe

[Anonymous Coward]

Oh geez, not you again.

Re:Electric Universe

[Anonymous Coward]

Please see: http://mnras.oxfordjournals.org/content/261/1/L21.full.pdf

TL;DR: Accounting for electromagnetism does not explain the 'strange' velocity curves of galaxies.

Re:Electric Universe

[Anonymous Coward]

Do you have an example that compares the fits (with an without the proposed EM force) to data?

Re:Electric Universe

[Jaborandy]

Thank you for the link, AC.

I saw two errors so egregious in the first three pages that I can dismiss that paper immediately. First the authors claimed that stellar gasses need to be sufficiently ionized that magnetic field lines could be frozen in them. This represents a fundamental misunderstanding of electromagnetism. These people could not possibly give fair treatment to an electromagnetic theory with such a basic misunderstanding. Second, they claim that obviously stars are not affected by the magnetic fields, and therefore they can falsify the opposing claim by demonstrating that gasses and stars move together. The plasma universe theories require a corresponding adjustment to our understanding of the stars themselves as strong electrically charged objects themselves, but more importantly the modeling of the flow of current is the key to understanding the electromagnetic forces acting on the gasses and stars.

Those folks took down a straw man.

--Jaborandy

Re:Electric Universe

[Anonymous Coward]

First the authors claimed that stellar gasses need to be sufficiently ionized that magnetic field lines could be frozen in them.

The regime of conditions where frozen flux works in plasma physics is pretty basic plasma physics and has been heavily demonstrated experimentally in both laboratory and astrophysical plasmas.

The plasma universe theories require a corresponding adjustment to our understanding of the stars themselves as strong electrically charged objects themselves, but more importantly the modeling of the flow of current is the key to understanding the electromagnetic forces acting on the gasses and stars.

And quantitative predictions made as such seem to contradict direct measurements of currents by space probes, and of electric fields by spectroscopy. Although quantitative predictions are difficult to come by with such theories, as most proponents seem to waste way too many pages of text putting words in the mouth of astrophysicists than actual talking about theories in any detail.

It IS God.

[Anonymous Coward]

It's god. Now that's nerdy.

Perhaps dark matter is not actually matter

[Anonymous Coward]

A simpler explanation is that the “dark matter effect” is an immaterial force analogous to gravity or magnetism that we have yet to detect. We know from direct observation that matter has a gravitational effect on light. Has anyone yet explored the corollary that the light permeating the universe must have equal effect and opposite on that matter? The theory of relativity nicely explains what happens when matter is transformed into energy, but what happens to that energy? Current cosmology seems to assume that it just dissipates as the universe expands. If the big bang theory is wrong and we actually live in a steady state universe, that energy must be transformed back into matter or the result is “heat death” in deep time. Experimental physicists may have just not been looking in the right place yet.

Re:Perhaps dark matter is not actually matter

[TMB]

The energy density in the universe from light is much less than the energy density from baryonic matter, which is in itself much less than the total matter energy density of the universe (which is why we infer the existence of non-baryonic, or "dark", matter).

Heh, maybe it is superfluid?

[PaulBu]

Just partially kidding...

Paul B.

is it real?

[Anonymous Coward]

isn't there a good chance that the dark matter theory is incorrect, and was created to account for an error in certain physics equations? Mb dark matter is so invisible because it doesn't actually exist?

Re:is it real?

[Livius]

Of course there's a chance, but it doesn't look like a 'good' chance. If the dark matter hypothesis is wrong, it's likely wrong yet highly insightful in the same way that Newtonian gravity is wrong.

Re:is it real?

[Anonymous Coward]

Physics is a model. It does not "exist" in the same sense as we assume a wine bottle and cork in your hand exist (leaving aside the issue of biological basis). It is a collection of abstractions at varying levels which allow us to model things which "exist".

Science does not deal in "right" or "wrong" just in "best fit".

Re:is it real?

[Anonymous Coward]

When I was taking Astronomy classes back at the uni (some 20 years ago, sigh) -- my professor said that dark matter did not feel like. That pretty much every time you have to start resorting to adding exotic explanations for your observations, onw shouls consider if ones base model or assumptions are wrong. He felt that the whole concept of dark matter could be such a candidate. That our experimental observations of gravity was limited to solar system scale, and maybe gravity works slightly differently over larger distances than that

Re:is it real?

[BlackPignouf]

For my next exam, if I get x==3 as a result and I know it should be x==100, I'll just define dark_x = 97.
Done!

Patches on top of patches

[Anonymous Coward]

I've never really been convinced that Dark Matter was the magical fix to the standard model it's cracked up to be.

It seems really hackish to me. Although in all honesty, I don't have the slighest hint of a clue what I'm talking about. I'll just wait on the sidelines and see what happens.

Certainty in Science

[Jaborandy]

It really bothers me to see quotes like this one: "There is more dark matter in the Universe than visible matter, but it is extremely elusive."

That's so matter of fact, and leaves no room for the possibility that the theory of dark matter is wrong. I feel that the certainty level around our understanding of this topic is low enough that it isn't fair to competing theories to say things like that as if they are observed fact. In fact, we've never detected dark matter. We infer its existence from a number of things that don't add up gravitationally without it, indicating we're missing something. Dark matter that interacts gravitationally allows us to model a universe that adds up, if only this invisible stuff were distributed just so.

This article shows yet another data point indicating that dark matter may not exist, because of how it continues to not react with stuff, just as it would if it weren't there at all. I don't mean to say that it's 100% wrong, but I think it's unfair to say with 100% certainty that it's true either. Shouldn't we as scientists be more careful with our words, and say that dark matter is BELIEVED to make up more of the universe than does visible matter, based on our current leading theories? I think being careful with what we know and how well we know it is important to maintaining trust with the public and with each-other.

--Jaborandy

Re:Certainty in Science

[Anonymous Coward]

Indeed. I've always wondered why there's an automatic assumption that matter of some sort must be causing these excess gravitational effects that are popularly associated with dark matter. I believe there's just as much merit to the idea that our understanding of gravity is simply wrong, and that it can exist absent of matter. I would think of it as space time curvature that is inherent to the universe. Matter would naturally "fall in" to these wrinkles of the fabric in space time, and perhaps that is what causes the cosmic web structure we observe in the universe today.

Re:Certainty in Science

[Anonymous Coward]

I strongly disagree. This observation is very cool and useful.

The article points out an important aspect of what dark matter is and how it interacts and will help identify the cause of the extra gravitational attraction around galaxies. This discovery gets me thinking more about more possibilities for doing more observations to identify what it is. The fact that it keeps moving not with the galaxies indicates that it is more likely particulate matter, ghost fields, or some string theory related object and less likely a generated immediate field emanating from the black hole at the galatic center, or a hidden form of planetoid or sun sized objects.

But I do wonder if it exists or if it doesn't exist.

Even if it doesn't exist, I am curious what is causing this gravity thing we are calling dark matter to affect things.

Re:Certainty in Science

[Anonymous Coward]

You can be fairly certain that the journalist was less careful with their words than the scientist.

Re:Certainty in Science

[Anonymous Coward]

The quote that bothers me somewhat is this one:
          The data here is on the very edge of reality, built on too many assumptions.

Data is data. Assumptions are the stuff of models and theories. Don't mix the two.

Re:Certainty in Science

[Bite The Pillow]

Dark matter is stuff that behaves like matter but isn't visible. Dark energy is stuff that behaves like energy, but isn't visible. When you know that, it makes sense.

"Dark Matter" is a placeholder for "whatever the hell is causing this".

There is more "whatever the hell is causing this" than visible matter.

That is so matter of fact, and it leaves no room for... wait, it leaves a lot of room for a description of "whatever the hell is causing this".

This article shows yet another data point indicating that dark matter may not exist, because of how it continues to not react with stuff, just as it would if it weren't there at all.

Nope. The images contain evidence of dark matter, because the matter we *can* see doesn't behave the way it should if there were nothing else that we *can't* see.

Re:Certainty in Science

[khchung]

The quote that bothers me somewhat is this one:

          The data here is on the very edge of reality, built on too many assumptions.

Data is data. Assumptions are the stuff of models and theories. Don't mix the two.

Data is nothing if you do not have any way to interpret it. Models and theories provide the context for interpreting the data.

It is like saying "bits are bits, assumptions are the stuff of encoding and decoding". Problem is, without any assumption to decode your bits, it would be as useful as any random noise. The fact that we can have a conversation here is because I (or rather, my browser) made the assumption that the bits are encoded with a certain pattern, and so did you.

Without any assumptions, models, or theories, the signals we received from Hubble would be no different from random noise.

Without the assumption that the photons came from a distant galaxy, we cannot form the image we can see.
Without the assumption of what they saw were the result of the collision of two galaxies, it would just be a bunch of stars in a strange shape.
Without the assumption of the current model of our universe, we cannot guess what would be the most probably original form of the two galaxies.
Without the assumption of the Theory of Gravity, no one can make sense of what could have happened when two galaxies collide, and thus compare with this observation.
Without the assumption of the model of gases and stars, we cannot reach the conclusion that gases should interact and slow down, while stars would not.

The problem is, with our currently best assumptions, models and theories, those that are able to explain most of our observable universe, we found that it would require the present of some undetectable matter in all the galaxies to make everything consistent -- hence "dark matter".

Yeah, you can claim that is too many levels of assumptions. Feel free to build up your own that could consistently match all the known data even better than the one commonly used.

Re:Certainty in Science

[Livius]

Scientists (with perhaps a few exceptions) leave room for the possibility that the theory of dark matter is wrong. Uninformed journalists - not so much.

Given how old this 'insight' is, I think it comes from the latter group.

Re:Certainty in Science

[Altrag]

There isn't any such assumption. Go look up MOND. Dark matter is just the best match we've come up with so far that fits the data.

So anyone who isn't actively researching exactly that topic may as well go with the prevailing best match. It might turn out to be wrong, but its at least less wrong than the next best match. And certainly less wrong than just ignoring the data because you don't happen to like the term that was coined to describe it.

Re:Certainty in Science

[Anonymous Coward]

That's a lot of talk to completely miss the point.

Re:Certainty in Science

[dbIII]

That's so matter of fact, and leaves no room for the possibility that the theory of dark matter is wrong

Yes.
Gravitational effects show that something is there which we cannot see.
That's the bit that's treated as a matter of fact. What that stuff actually may be is where we don't have anything that can be treated on the level of facts.
So we are certain that something is there but not certain as to what it is, apart from ruling out a lot of things that should make sense but don't fit (dust, brown dwarfs etc), which is why this stuff is so mysterious.

Re:Certainty in Science

[Anonymous Coward]

because the matter we *can* see doesn't behave the way it should

Or, it behaves exactly as it's supposed to (it doesn't really have a choice, either), and our current understanding is widly wrong.
Perhaps there doesn't need to be any dark matter or dark energy to explain this. But then again, that's a whole lot of interpretations and speculations right there.

Re:Certainty in Science

[Bengie]

The reason people assume Dark Matter exists is because the implications of it not existing is even more absurd. It's the lesser of two evils, by a lot.

Re:Certainty in Science

[Bengie]

Then the point was not well made, because it looks to fit perfectly.

Re:Certainty in Science

[Bengie]

Man1: Man, I'm only getting 25mpg, and I normally get 35mpg
Man2: Ever think that our understanding of the chemistry is wrong, and the gasoline is losing energy in a way you never expected?
Man1: I'm going to go with the gas station added an ethanol mix which reduced the energy density
Man2: But what if our current understanding of chemistry wildly wrong, and you're car is special and shows our flawed understanding?

Man2 could be correct. Hell, anyone could be correct about anything, there is no real 100% or 0% confidence.

Re:Certainty in Science

[Anonymous Coward]

It is obvious the poster meant to not confuse data as an assumption, not that they are unrelated. Reading comprehension, people.

Re:Certainty in Science

[cold fjord]

Make that MOND/TeVeS.

Fitting the data isn't simply a question of the fitness of the theory, but also of the effort involved in applying the theory to the data to see if it explains it. TeVeS predicts gravitational lensing, for example, but someone had to figure that out. How much more could it explain if it was pursued at more than the level of a minor hobby? Hard to say. Theories besides Dark Matter get little in terms of funding, and going against mainstream science is risky for a career even if mainstream science is wrong on the issue.

Re:Certainty in Science

[Anonymous Coward]

Theories besides Dark Matter get little in terms of funding, and going against mainstream science is risky for a career even if mainstream science is wrong on the issue.

Except MOND and TeVeS are still mainstream science, and doing research in one of those fields is not risky for your career in the slightest (unless you are trying to build a career in a vastly different field). Even if they don't get much manpower, which is true for theorists and astrophysics in a lot of subfields, they get plenty of moral support and curious interest from the rest of the physics community. This is why there are still whole research groups getting funding for it.

Contradicting leading theories doesn't exclude a person from mainstream science, and in fact a lot of researchers will write papers on new ideas that directly contradict theories of varying levels of acceptance. This is one way of getting attention as a new researcher, and the only reason not to want that when starting a science career is if you are not actually that good and don't want people to notice how crappy your research is.

Re:Certainty in Science

[vemene]

Shouldn't we as scientists be more careful with our words, and say that dark matter is BELIEVED to make up more of the universe than does visible matter, based on our current leading theories? I think being careful with what we know and how well we know it is important to maintaining trust with the public and with each-other.

Even better, non-lazy journalists could use the specific technical term "hypothesized" instead of the more-familiar "believed" and we can eventually increase scientific literacy in the general public a wee bit.

Re:Certainty in Science

[Anonymous Coward]

http://www.scilogs.com/the-dark-matter-crisis/2015/03/20/can-one-say-anything-even-the-most-obviously-wrong-things-to-discredit-an-alternative-to-the-standard-model-an-incident-cosmology-at-caltech/

Re:Certainty in Science

[Anonymous Coward]

Because you found an example of some professor set in his ways, that must mean everyone in the community rejects it? Professors and scientists are human, and can become attached or and set in ways, and not just about cosmology. I've worked places that had a professor, each, rejecting general relativity, MHD, QFT, and non-physics things like AIDS, among other things. They still stick around because they produced meaningful work, or were decent teachers, despite the stupidity of some the things they would say on very specific topics.

Doesn't change that talks on alternative ideas are welcomed and popular. And the professor in your link was right on one thing, that certain topics do tend to accumulate crackpots. But the difference between a crackpot and scientist isn't just about making mistakes, but one of attitude and lack of ability to communicate preventing learning from mistakes. With a bit of humility (resisting yelling about everyone else being wrong), some downright crazy ideas can be presented and capture interest, at least as a curiosity.

Re:Certainty in Science

[Anonymous Coward]

I do not have personal experience, but the people writing the blog are the primary MOND proponents so I assume they choose to write about representative experiances they have (you can read other posts to see more discussion of that type of treatment). Milgrom also said in an interview that his idea was not popular from the beginning:

How was MOND first received by the scientific community?

I did encounter much opposition and sheer disregard, and this was against my expectation. I was surprised that people thought that this was not a legitimate avenue to explore. Many times I heard people say that it is too early to start considering such heretical ideas. Why? I wondered. I thought it was legitimate to consider anything.

http://www.americanscientist.org/issues/pub/dark%E2%80%90matter%E2%80%90heretic

From my perspective it is essentially your word (an AC) regarding the current culture surrounding cosmology vs. theirs. I don't know.

Re:Certainty in Science

[Mattsson]

Shouldn't we as scientists be more careful with our words, and say that dark matter is BELIEVED to make up more of the universe than does visible matter, based on our current leading theories?

A very good point, and one that often is missed when talking about scientific subject.
But one also has to differentiate between what is reported that a scientist, a group of scientists, or a scientific study says, and what they actually say.
Quite often, what is reported is a complete misinterpretation of what was said, or is being intentionally made wrong in order to make a sensationalistic headline.

One other thing that is often missed or ignored by media reporting on scientific matters is that there often are different possible explanations, and that different scientists work on different studies of the same thing at the same time and might come to conflicting conclusions that are both as probable.
Scientists or science is often referred to as one coherent group with one mind. =P

Time for a new idea

[Anonymous Coward]

It seems to me that whatever is going on, we have no clue.

Calling it dark matter and dark energy might be doing us a disservice. Maybe this dark whatever is the 21st century equivalent of ether.

on the very edge of reality, built on too many ass

[Sla$hPot]

umptions... Says it all :P

Alien energy collection systems

[Anonymous Coward]

Clearly, the solution is that an Alien Civilization (which I predict is only slightly younger than the universe) has setup a near invisible (to us) energy collection system that collects gravitational energy. The slowing/speeding up of regular matter that we see is a direct result of the impact of this colossal collection system on our local universe.

Easy peasy. I welcome our new energy collection overlords.

Awful, awful science reporting

[disputationist]

Theorist with publications in dark matter here. This aspect of dark matter is not something new or a "mystery" but something that has been assumed for quite a long time. The alternative to this, "self interacting dark matter" is not entirely ruled out by observatins and explains some issues like the core-cusp problem but it's generally disfavored.

Re:Awful, awful science reporting

[Anonymous Coward]

The result is what I call the “scientific surprise” two-step: (1) When defending the plausibility of your results, you emphasize that they are just as expected from a well-estabilished scientific theory with a rich literature; (2) When publicizing your results (including doing what it takes to get publication in a top journal, ideally a tabloid such as Science or Nature) you emphasize the novelty and surprise value.

http://andrewgelman.com/2014/08/01/scientific-surprise-two-step/

Re:Awful, awful science reporting

[Bite The Pillow]

âoeA previous study had seen similar behavior in the Bullet Cluster,â said co-investigator Richard Massey of Durham University in the UK. âoeBut itâ(TM)s difficult to interpret what youâ(TM)re seeing if you have just one example. Each collision takes hundreds of millions of years, so in a human lifetime we only get to see one freeze-frame from a single camera angle. Now that we have studied so many more collisions, we can start to piece together the full movie and better understand what is going on.â

Is that not new?

Very few things in real research are genuinely new, but confirmation of prior examples, often in greater numbers, bolsters the field in general.

Is there something you can point to that already did this : "focused on 72 galactic cluster collisions from all angles and at different times during their collisions"?

Also possibly fictious

[Karmashock]

Here some someone with a propeller beanie on his head will tell me that dark matter must exist because "math"... which is fine only "math" is not actually evidence of something being there absent emperical evaluation because even if the numbers add up a certain way so do orbital epicycles.... and they were bullshit.

A pitfall of the "math" argument is that if you have some very clever people come up with some very clever theories they can confuse Tolken-like world building with "reality".

The justification for dark matter is unexplained gravity. And the gravity is something we know exists because we are seeing the speed at which galaxies spin around and there shouldn't be enough mass to explain that speed. And that extra mass because we can't find it is called "dark matter"...

Well, that's great... only that doesn't mean dark matter exists. It could mean our theories of gravitation are wrong or any number of other things.

same thing with "Dark energy"... which in so far as I've figured out only exists because galaxies are accelerating away from each other and we have no idea what could cause every galaxy to propel itself at speeds like that except some other unexplained energy and that's what is dark energy.

In both cases it just sounds like they don't have enough observational data to really have a valid cosmological model. And I would much rather them make that admission then talk to me about "dark" whatever.

Re:Also possibly fictious

[Anonymous Coward]

Feels like you onto those dark constellations were everyone can star a new. Shadows of gravity, mysteries of movement faster than eye can see, pain is only a state of mind, breeders are to be converted or killed. We keep what we kill and see the universe without confusion of many faiths, cloths of morality. Onwards to replenish the troops!

Re:Also possibly fictious

[steelfood]

Yes, dark matter and dark energy are convenient constructs to make our existing models fit.

When they find data that doesn't fit the constructs, then scientists have two choices:
1) Change the constructs
2) Change the model.

They're usually going to choose #1 because Occum's Razor prefers #1. They won't go with #2 until there's a sufficient body of evidence that the constructs are completely wrong. Until then, it's just going to be more tweaking and retweaking of the constructs.

Now, when I say "they", I don't mean scientists as a body. Usually, it's just one guy pushing a wild theory that gains traction over time with more evidence and more calculations.

But this is science. It's normally iterative, not revolutionary. Except when the data calls for it.

Re:Also possibly fictious

[Karmashock]

If I were handing out funding grants, I'd be less interested in doing it on the dark matter energy research and more interested in throwing the money at seeing if there isn't a model that doesn't require such "constructs".

The whole thing reads like epicycles to me. Those curly cue micro orbits that they used to think our planets traveled in to explain their movement.

And that only went away when they realized the earth wasn't the center of the solar system but rather it was the sun itself.

I'm not an astrophysicist... but I have actually had education in astrophysics. I mean, I could personally calculate all the orbits of the planets using raw observational data. I know the equations and how to use them. I also know the history of that science.

And all this dark matter/energy stuff just sounds like epicycles all over again.

Both dark matter and energy are more than a construct. It radically effects the nature of the model.

The model cannot explain why the galaxies are spinning around so fast which leads them to believe "dark matter" and then they don't know why the galaxies are ACCELERATING away from each other and so they say "dark energy".

That's more than a construct. That is GALAXIES spinning around faster and galaxies accelerating away from each other. That's huge.

discovering a discrepancy like that should result in a complete reevaluation of the entire model... not just saying "well, the orbits of the planets go along these little curly cue orbits for no reason".

We have not fought a single particle of dark matter. They're saying in some reports that 70 percent of the mass in the universe is dark matter. And we haven't got our hands on so much as a speck of it? How likely is that?

I don't think dark matter or energy are answers to the question.

It is just an admission that they don't know why the galaxies are spinning around that fast and they don't know why they are accelerating away from each other.

That's it.

Nothing more.

Just that.

And so dark matter/energy is no answer. It is of no significance.

Re:Also possibly fictious

[radarskiy]

"The justification for dark matter is unexplained gravity"

You imply that this is the *only* justification. Is this because you are unaware of the rest pf physics or because you are trying to mislead others about the rest of physics?

Re:Also possibly fictious

[Anonymous Coward]

The whole thing reads like dark matter to me. Those spheroids of invisible matter that they used to think our galaxies traveled in to explain their movement.

Re:Also possibly fictious

[Anonymous Coward]

I'm glad other nerds believe this. I thought I was the only one.

Re:Also possibly fictious

[Anonymous Coward]

Here some someone with a propeller beanie on his head will tell me that dark matter must exist because "math"... which is fine only "math" is not actually evidence of something being there absent emperical evaluation because even if the numbers add up a certain way so do orbital epicycles.... and they were bullshit.

Yeah, what a great start to demean people smarter or know more than you.

A pitfall of the "math" argument is that if you have some very clever people come up with some very clever theories they can confuse Tolken-like world building with "reality".

It sounded like a "pitfall" to you because you don't know how it works.

Ever heard of how they broke Engima during WWII? (Or have you watched The Imitation Game?) By your logic, after they have cracked the Enigma, you could also said that they might have just came up with some "very clever" way to make it looked like they cracked it, but in fact all the "decoded" messages were all wrong.

All the rest only showed that, as another poster said, you are unaware of "the rest of physics".

You are just like the general in the movie, where he was just about to break the machine, and Turing hopelessly said "You would never understand!".

Re:Also possibly fictious

[Karmashock]

I'm not demeaning people smarter than myself. I'm demeaning people more myopic and pedantic than myself.

I found nothing in your post but baseless insults... do you have even a thought worth contributing or was that all you were able to offer? Because any halfwit child could muster that much.

Do better.

Re:Also possibly fictious

[Karmashock]

Given that they've never seen it or directly detected it and that it has only been assumed to exist at intergalactic distances due to unexplained gravitational discrepancies... yeah, that is my understanding.

Do you have further information or can I just expect vague shit posts and trolling from you?

Offer something constructive to the discussion or eat all the dicks.

Every last one.

Re:Also possibly fictious

[Anonymous Coward]

Given what's observed there are three possibilities:

1) Additional source terms in General Relativity stress-strain tensor [Cosmological constant; Dark Energy; Dark Matter]
2) Additional [i.e. Higher order] terms in curvature tensor
3) Rejection of General Relativity as the descriptor of large, massive, fast-moving objects

in order of increasing magnitude of the change. The normal and by far least-extraordinary approach is (1). Make some not a priori unreasonable assumptions (there's particles with mass but no electric/weak/color charge or moments), plug them into the field equations, find out what they do, and it turns out that the idea of a pressureless perfectly-cold-gas works... depressingly well. There are enough minds applying themselves to considering additional forms of the lefthand side of the Einstein equations that they routinely hold conferences; I had a hard enough time understanding the Ricci tensor, so I won't pretend to know squat about that.

I gather you're proposing the rejection of General Relativity. Any theorist will tell you you're mad because General Relativity is the more or less inevitable conclusion when you find the most general form of what differential geometry permits and apply the restrictions based on what we observe. Any experimentalist will tell you that every test simply rules out alternatives to it (such as compactified dimensions, MOND, etc), more and more stringently. The problem has become: any alternative to General Relativity must look exactly like General Relativity, except under certain extremely difficult to test circumstances. So generally, as with most proposed Grand Unified Theories which must contend with the similarly stubborn accuracy of the Standard Model, some symmetry-breaking or effect is proposed to occur at a stupid high energy scale or similar and we have to rule out or detect the miniscule leading perturbative term of it.

Re:Also possibly fictious

[Karmashock]

Fine... we'll play the epicycles game a bit longer. When we're both in Hell, and the mysteries of the universe crack wide... We can see which of us was right.

I think this might be a thing were they play with it for a few more generations and then realize they had made some simple core assumption that was wrong. And by inverting that assumption everything else falls into place.

But what do I know... dark matter dark energy dark mathematics with dark chocolate and dark stormy nights.

Re:Also possibly fictious

[radarskiy]

Particle physics predicts certain weakly-interacting particles (http://arxiv.org/abs/hep-ex/9802007) which just so happen to have properties that coincide with the WIMPs which are one of the possible predicted particles from cosmology. There is data coming in from non-gravitational experiments (http://www.sciencemag.org/content/327/5973/1619) though not a lot so far. However, conformation of the particles' existence is not necessary to refute your claim there that there are only gravity-based predictions.

Re:Also possibly fictious

[Altrag]

Plan 1: Come up with reasonable hypothesis. Build math that works with it. Build detectors to test it. A negative result is still a result.

Plan 2: Throw up our hands because if we can't immediately get an answer then why even try.

You seem to be preferring plan 2.

And yes, there is research into alternate theories. Plenty of it with MOND being the biggest/most well-known competitor. But so far none of them have come close to matching the accuracy of dark matter theories so there's no much point spending 3/4 of a reporter's word budget describing them. Interested people can Google shit themselves (or even arxiv some actual papers if they've got the skills and knowledge to understand them.)

Dark energy is a completely different beast. Nobody has any idea what the hell to do with that. The data pretty much matches Einstein's cosmological constant from GR to a decent degree of accuracy but nobody really knows what that means or how to make predictions based on it, never mind measuring the results of such predictions.

Re:Also possibly fictious

[Anonymous Coward]

>Usually, it's just one guy pushing a wild theory that gains traction over time with more evidence and more calculations.

This, a million times. Hawking was an arrogant little shit that nobody liked so they threw black holes at him to shut him up and take him down a notch. He proved black holes with, well, MATH. Nobody liked it (or him) and it took a while until everybody realized he was right. Now it's gospel.

Nobody believed in germs for a long time, either.

Re:Also possibly fictious

[Altrag]

http://en.wikipedia.org/wiki/Dark_matter#Observational_evidence

That was hard.

Re:Also possibly fictious

[Karmashock]

Neither of your sources actually found dark matter.

I'm going to have to reject your attempt to browbeat me until you can show that there is evidence of dark matter outside of the hypothetical or the gravitational observations of distant galaxies.

Re:Also possibly fictious

[BlackPignouf]

You say "Observational evidence", I say "Our models are wrong".

Re:Also possibly fictious

[Anonymous Coward]

And by inverting that assumption everything else falls into place.

Entire teams of researchers are working on changing the assumptions and developing new theories of gravity. It is not that simple as just turning off an assumption and getting something better, as a lot of proposed changes are found to not be self-consistent, and even when self-consistent models are found, they don't fit observations as well as dark matter. I've sat through a number of alternative gravity talks, which get far more attention that a lot of other topics from physicists (at conferences, or at a colloquium at a dept.) curious what progress has been made. But the results so far typically only match a single category of observations of the several that dark matter matches, and involve theories that are just as arbitrary, if not more, in terms of new assumptions needed. The speakers defending the new theory will often flat out state that their theory still falls short of what dark matter can do.

Of course there is the possibility that some other simpler theory exists and hasn't been discovered yet, but that is true for every single concept and corner in science.

Re:Also possibly fictious

[Karmashock]

That's fine... keep making epicycles... maybe that is just how the universe works. In all sincerity, how would I know?

Just know I'll be over here chuckling when you find dark magnetism, dark weak nuclear force, dark strong nuclear force, and turtles all the way down.

Re:Also possibly fictious

[Karmashock]

Except I referenced that already. Go back and read my post again... I can't be bothered to repeat myself if you can't be bothered to read my post the first time.

Re:Also possibly fictious

[Bengie]

Then they're completely wrong, to the point that they do not work at all for anything. The fact that my computer seems to work must be dumb luck and was not purposefully designed using scientific theory.

There is gravity in the middle of empty space with no detectable baryonic matter for hundreds of millions of light-years in all directions. You explain that without an unseen new matter. That's right. There are massive voids in space, where we can see the galaxies in the background behind them perfectly clear, but we can detect gravitational lensing within the void. Even if the lensing was caused by dust, the sheer amount of lensing would mean an amount of dust that would be easily detectable. You could also say it's a bunch of blackholes that got ejected from their host galaxy and just so happened to not drag any dust along with them. Even if you could accept that, the lensing is so spread out, it couldn't be point sources.

And there is no evidence that smoking is bad for you. Our models are wrong.

Re:Also possibly fictious

[Anonymous Coward]

So what's your point? You complained that physicists put too much faith in math and that it might just be a matter of simply changing one of the assumptions. But this is flat out wrong in the sense that physicists from the start have been considering it might be flaw in more fundamental theories. And despite decades of growing evidence pointing more toward the dark matter theory, physicists still continue to pursue alternatives just in case.

There is nothing special linking this particular theory to epicycles, beyond your gut feeling you don't like one explanation over another. The possibility that there is a better theory out there and that current ones are wrong is applicable to everything in science. In the meantime, most areas of science have moved forward by pursuing ideas proposed to fix disagreement from math and observation.

Re:Also possibly fictious

[Anonymous Coward]

"And there is no evidence that smoking is bad for you."

I'd watch out aligning yourself with any medical research claims... Anyway your version of that claim is likely too simplified to be true.

Re:Also possibly fictious

[radarskiy]

"Neither of your sources actually found dark matter."

Your original claim wasn't about whether it has been conclusively found or not, therefore the fact that my responses do not address such a claim is as irrelevant as it is unsurprising.

Your actual claim was "The justification for dark matter is unexplained gravity" to which I responded with a non-gravitational justification.

Re:Also possibly fictious

[Altrag]

And you apparently still didn't bother reading that Wiki article before running your mouth.

If there was only one piece of evidence then sure, you can find multiple answers. But there's multiple pieces of evidence which greatly restricts the number of possible answers.

You asked for further information, I showed you where to find it. If you refuse to bother reading it then that's your problem. Its amazing how many people want to think that not having ALL the answers is equivalent to not having ANY answers.

Re:Also possibly fictious

[Karmashock]

Suppositions are not evidence of anything.

Re:Also possibly fictious

[Karmashock]

I prefer honesty.

What you seem to be saying is that any old bullshit is viable in the absence of something better.

The claims of dark matter/energy are misstatements of what has actually been detected.

They have detected neither matter nor energy. What they have detected are effects that so far as we know can only be caused by matter and energy... which we cannot detect and don't especially understand.

That is not the same thing.

I would be much happier with the whole thing if rather then referring to this stuff as dark matter they simply referred to it as the gravitational anomaly.

Or if you prefer... call it dark gravity and dark acceleration.

To imply that the gravity must be caused by matter and the acceleration must be caused by energy is an assumption.

The dark energy for example could be the expansion of the universe or something. No acceleration but rather the universe just expanding. Space increasing between galaxies rather than galaxies moving away from each other.

And as to dark gravity... when you say that your mass calculations are off by 70 percent which is what all this dark matter stuff says, it means your estimates as to what you can actually see and not see is not reliable.

It could be as simple as there just being more matter in those galaxies than people believed... normal matter. Not dark matter. Just more of it than anyone had guessed. Perhaps 70 percent more.

Re:Also possibly fictious

[Anonymous Coward]

I prefer honesty. What you seem to be saying is that any old bullshit is viable in the absence of something better.

You seem to fundamentally misunderstand how science or even inductive logic works, yet want to blame scientists for this. All science is about having the best explanation possible given current knowledge, with the possibility it will be rewritten at a later date as the result of new ideas or observations. Scientists are quite aware of this, even if they don't waste time repeating the most basic ideas of science every single time they talk about something. To single out those working on dark matter is betrays your lack of understanding of this.

Space increasing between galaxies rather than galaxies moving away from each other.

That is what the expanding universe is with an expanding metric. That is how we used to think it works, but it no longer agrees with more detailed observations. You should probably read an intro section of a text book or even Wikipedia before getting much more judgmental about "simple" alternatives.

It could be as simple as there just being more matter in those galaxies than people believed... normal matter. Not dark matter. Just more of it than anyone had guessed. Perhaps 70 percent more.

20 years ago this would be true, when searches for MACHOs were just ramping up. But since then, a lot of upper bounds on various types of ordinary matter have been determined that are way too low. And better observations of the CMB matched lamda-CDM predictions quite well, excluding normal matter with nothing so far to suggest that model is wrong. And there is no presumption that we've found all of the normal matter, as the same results show there is a large amount of normal matter to be discovered too.

Re:Also possibly fictious

[Karmashock]

Okay, then what is propelling GALAXIES away from each other? Do you have any fucking idea how much energy we're talking about with that?

What could possibly be the source of that kind of energy? Fucking unicorn magic?

Simply labeling it dark energy "aka energy we can't find and don't know anything about" isn't actually helpful. You don't in fact know whether any energy is being expended. All you know is that there is an apparent effect and given your other knowledge that effect would require insane amounts of energy.

The thing is you don't know. They don't know.

And all your pathetic attempts to browbeat me on logic are covering over like a bad topee is that YOU DO NOT KNOW.

And that's all I'm asking for here, you complete waste of oxygen. An admission that people don't know what the fuck is going on. And they don't. And that's okay.

Keep investigating it. Keep coming up with theories. Keep doing the experiments. Keep doing the math. But don't tell me about your fucking hobbit energy or your wizard matter or any other shit you just made up to cover for the fact that there are things going on that you do not understand.

Re:Also possibly fictious

[Anonymous Coward]

An admission that people don't know what the fuck is going on.

You mean like in nearly every introduction to the topic, in the very summary of things like textbooks and Wikipedia articles? Dark energy is just the name for a slight change to the FLRW metric that does an extremely good job of matching observations. There is no hiding of how open ended the question is of what causes that term, and while there is a long list of potential ideas what could cause that extra term, there is very little claiming of certainty of which particular idea is best.

And that is rather different than dark matter, where the original long list of equality potential ideas has been significantly pruned with a much largest and varied set of observations. Lumping dark matter together with dark energy, or jumping back and for between the two interchangeably in your tirade just continues to show a lack of awareness of the actual research despite your intensity.

And all your pathetic attempts to browbeat me on logic are covering over like a bad topee is that YOU DO NOT KNOW.

And you've moved on past logic, and seem to be left with an emotional response, which doesn't help resolve the issue that you are making claims with such insistence about topics you display complete lack of knowledge about. There are volumes written about how many unknowns there are with dark energy, and there is an even large volume of written material at all levels on what is known about dark matter, but you continue to insist that the former is being hidden and closing your ears to the latter. This is no longer a rejection of reality in deep space, but a rejection of the reality right here on Earth and available to you for little effort over the internet.

Your questions about the details of theories and ideas around them could easily be addressed by things already written and simple websearches. There is no point in copy-pasting or paraphrasing such material for the nth time on the internet only to be ignored again.

Re:Also possibly fictious

[Anonymous Coward]

And better observations of the CMB matched lamda-CDM predictions quite well, excluding normal matter with nothing so far to suggest that model is wrong

I do not think the first part is true, they had to change model parameters post-hoc to get the fit. It was not a prediction. I also do not think the second part is accurate. "Normal matter" was not excluded, only that known sources of normal matter cannot account for observations. Everyone knew that before so I'm not sure what it has to do with anything. Disproving hypothesis A does not let you conclude hypothesis B.

Re:Also possibly fictious

[Anonymous Coward]

Everyone knew that before so I'm not sure what it has to do with anything.

Then maybe you need to look into the subject, as it explicitly excludes baryonic matter. And while there were some parameters that were fitted as a result, they model is not free enough to allow anything to be fit, just as a theory predicting a quadratic relation might need 2-3 parameters fit, but would be rejected if the results turned out to be linear or cubic, or any of a bunch of other possibles (and there were other more exotic ideas for the CMB that failed).

Re:Also possibly fictious

[Altrag]

So what would you rather call it?

The term "dark" is used specifically as short hand for "we don't fucking know." Just because you don't understand (or refuse to acknowledge) that terminology doesn't mean some other terminology will be any better.

That said, for dark matter particularly, there is evidence beyond galaxy rotation to suggest that it is in fact an actual form of matter. We still don't have any clue what form that might be, but we do know some properties of it: It interacts gravitationally and it doesn't interact electromagnetically. Those two facts are pulled from actual observations not just "any old bullshit."

We generally assume other properties based on the math (for example, we often assume that its interacts via the weak force because the measured energy scales are very consistent, but that hasn't actually been proven via observation.)

That said, generating predictions using the math is not "any old bullshit." Its very systematically derived values based on what we already know. In the same way that we predicted anti-particles, the top quark and most recently the Higgs boson based purely on "well the math works out really nicely" and then a couple decades later we actually find the things we predicted.

Yes its "bullshit" in the sense that we don't have direct evidence of every single property, and yes there can be (and are) competing theories, but its not just pulled out of someone's ass for no reason either.

If you don't like the dark matter idea, go look up MOND. If you don't like MOND go look up something else. Or make your own theory (but remember it has to match existing, actual measurements as well in order to be useful.) There's plenty of possibilities.

Dark matter gets the most recognition because it so far is the best match for the (yes, limited) amount of data we've managed to collect so far. If we find evidence that the dark matter theory is wrong, it will be fixed or disposed to match the new observations. Its how science works.

But nobody anywhere (except you apparently) just wants to say "fuck it I don't know" and ignore the problem. Making a wrong step is better than making no step when you want to progress.

Dark Matter

[Anonymous Coward]

the real source of climate change.

Stars collision rarity

[jfisherwa]

What I find more interesting is why stars rarely collide? Is it just because all of the stars that were likely collide already have? Or is there some kind of polarity effect whereby most stars share a similar polarity, while non-reactive planets and gases are oppositely charged?

Re:Stars collision rarity

[WaffleMonster]

What I find more interesting is why stars rarely collide?

Too much empty space.

Re:Stars collision rarity

[Anonymous Coward]

Look up at the sky at night, which do you see more of, white stars or black sky? Very little of the space in either "colliding" galaxy is populated with stars, so in general they just go straight past each other.

Re:Stars collision rarity

[wbr1]

It is because space is BIG. Look at our galaxy, our closest neighbor is what 4.6 lightyears away. Even if you double the amount of stars in the same space, they will interact gravitationally sure, but colliding is like dumping 1000 toothpicks in random places in the oceans and having them collide.

Re:Stars collision rarity

[CrimsonAvenger]

What I find more interesting is why stars rarely collide?

Too much empty space.

This.

Consider that for two stars to hit each other, they essentially have to pass within one stellar diameter of each other (absent gravity, but they're moving at over escape speed relative to each other, so gravity won't enlarge that distance a whole hell of a lot).

So, one stellar diameter is ~1.4 Gm for Sol. Nearest star is 40,000,000 Gm away. If that nearest star were headed toward us (it's not), it's course would have to be within 0.01 seconds of arc of our Sun in order to actually hit it.

And stars farther away have an even smaller course window to be in to smack us....

Re:Stars collision rarity

[rubycodez]

You are right about that, even including all the trillions of stars the *average* density of the Milky Way is only 40 nucleons per cc (our best vacuum pumps do three hundred thousand molecules per cc!) That's a hella lot of mostly empty space

belief and faith

[turkeydance]

yeah. that could work.

dark matter only makes up 23%

[Anonymous Coward]

The article is mixing up dark matter and dark energy (two very different things)

Overall, dark energy is thought to contribute 73 percent of all the mass and energy in the universe. Another 23 percent is dark matter, which leaves only 4 percent of the universe composed of regular matter, such as stars, planets and people.May 12, 2011

More than that: it is a requirement!

[Roger W Moore]

Thought to be spread evenly throughout each cluster, it seems logical to assume that the clouds of dark matter would have a strong interaction

It would actually be completely illogical to assume that precisely BECAUSE Dark Matter is spread evenly through each cluster. If it had a strong self interaction then, just like matter, it would bump into itself and coalesce into clumps just like that other strongly, self interacting stuff we call matter. The fact that Dark Matter has a completely different mass distribution than ordinary matter is clear evidence that it does not have a large self interaction cross-section...and we have had direct evidence of this since the Bullet Cluster was discovered.

It's always nice to have more confirmation but since another recent story on the same site was talking about the "new" possibility of invisible Higgs decays to Dark Matter particles (something we looked for 15+ years ago at the Tevatron as well as the previous Run 1 of the LHC) I have to wonder if the writers of the site have suffered extreme time dilation for the past decade or two.

Re:More than that: it is a requirement!

[Anonymous Coward]

It seems logical for the strong interaction to be the case *going forward*. The sentence makes no claim as to how it got to that point.

Re:More than that: it is a requirement!

[Roger W Moore]

The fact that they are in 'clouds' is the problem though: you would not have those same clouds if they strongly interacted...and we have known about this for decades.

Re:More than that: it is a requirement!

[Roger W Moore]

My apologies - I did not realize that journalism used different rules for english and physics to the rest of us. That probably explains why I pay so little attention to most journalism.

Re:More than that: it is a requirement!

[Anonymous Coward]

That probably explains why I pay so little attention to most journalism.

Your attitude explains why our institution excludes "sci-fi" types. It will never fly in the real world.

News At 11

[fyngyrz]

Dateline: Millions of light years (even faster parsecs than the Kessel run)

Lede: Scientists in the Dark; Does it Matter?

Today scientists announced that they can't see anything happening with stuff they can't see, but think is there, because otherwise the math is no good. After receiving directions to his laboratory on the phone, I went to see an authority on dark matter. During the interview, Dr. Seemore Lichspittle told this Any Paper, Any Time reporter that the thing about dark matter that one has to understand is that "it goes to eleven." When confronted with the observation that the sensing instruments only had scales from 0-10, he responded "Yes, yes, that's exactly it. The numbers... the numbers only work out in the dark. When the instruments are off. Matter of fact, it's all dark, really." At that point the interview was cut short as two lab assistants in white coats hustled Dr. Lichspittle into his own custom white lab jacket. Late for an important meeting, no doubt. As he left, nodding, he called back "it's really quite dark." Food for thought! Leaving Arkham, I was struck by the picturesque beauty of the stonework, and very appreciative of the tight security. We can rest easy, knowing that national treasures like Dr. Lichspittle work in such a safe enviroment.

It could also be that our *MATH* is wrong

[Anonymous Coward]

No, not wrong calculation, but our understanding of *MATH* could be itself erroneous, and there are to possible reasons for it ---

1. Too short a civilization to understand "Right Math"
The modern humans, the one which can dabble in mathematics, exist as a species for only the past couple of thousands of years - and this really short time frame (relative to the age of the Universe) doesn't provide us sufficient time to understand / discover the "right" way to do math

2. Our innate disability
Perhaps the modern humans just ain't made to become the beings which is able to understand the ultimate knowledge

Back to the "Dark Matter / Dark Energy" discussion --- It could be that, as you said, the "Dark Matter / Dark Energy" does not exist, but it could also be that because of the wrong way of using math --- or even the math that we use today is itself wrong - we have boxed ourselves in and couldn't locate the true answer to the so-called 'mysterious mystery"

Same as zero point energy?

[grantspassalan]

Matter and energy are convertible one into the other. Is what scientists call dark matter/dark energy the same as "zero point energy"? Zero point energy is what is left in a container that has been emptied of all matter and then cooled to absolute zero. This energy has been measured and verified to exist. It pervades all space, including the spaces between the particles of atoms. Zero point energy is what limits how much a signal can be amplified and is the reason why liquid helium cannot be made solid without great pressure. There are many other known effects.

Re:Same as zero point energy?

[TMB]

That was what was first assumed. There's only one minor problem.

The amount of zero point energy is *120 orders of magnitude* larger than the measured magnitude of dark energy. And dark energy has about 3x the energy density of dark matter.

So, despite the fact that it looks like zero point energy, there's something else going on.

[TMB]

Re:Same as zero point energy?

[Anonymous Coward]

I would mod you up, but my opinion doesn't count for jack shit around here.

mysterious Dark Matter or just undetected matter?

[Anonymous Coward]

Why can't the "dark matter" just be asteroids to brown dwarf size clumps? Wasn't there news of several potential brown dwarfs in the sphere between here and the nearest previously detected star? So the stars whiz by and anything else with a similarly low proportion of mass to volume would too. What is the particle mass per unit volume of 100 cubic light years of gas vs 100 cu ly of star systems?

My field is nowhere near astronomy / cosmology so I am sure I don't have a sufficient knowledge of dark matter or anything related. Can someone explain how "dark matter" is something more mysterious than "undetected except at a very large scale" matter?

Best Explanation

[__aajxhe7746]

Dark matter doesn't actually exist

Re:Best Explanation

[slashmydots]

Wait......are you saying that we don't have the technology to measure all mass in the visible universe? Oh and the non-observable universe too, which makes perfect sense logically.

I had to dismiss your comment immediately

[Anonymous Coward]

I saw two errors so egregious in the first three pages that I can dismiss that paper immediately.

My pomposity meter went off when you implied the paper was longer than 3 pages. Oh, there is a fourth page, but all it has on it is 6 references. Anyway, I couldn't continue reading your comment because of this. Please correct your egregiously misleading remark and repost your comment so that I can continue reading it.

How sure are we...

[Brad1138]

That Dark Matter is a real thing and not just a "theory"? Do we have any proof yet? I know there is a lot of intel coming in on it, but it is hard to keep up with and/or follow.

Re:How sure are we...

[Anonymous Coward]

It not even a "Theory" yet... its a hypothesis that people are figuring out how to test for.

Re:How sure are we...

[Shados]

its an hypothesis and a model attempting to explain some weird stuff we're observing. Its probably wrong, but its a starting point. A bit like the early earth centric models of the solar system originally (that actually ended up giving the correct results, even though they were wrong)

Re:How sure are we...

[Altrag]

Funny thing is that epicycles weren't "wrong" (within the limits of measurement capability of the time.) They were just not the simplest way to do the computations.

To work with a sun-centric model you have to (in your imagination) translate yourself from the Earth to the center of the sun, figure out where the planets should be, then translate those planet coordinates back into Earth coordinates.

Epicycles is essentially combining those steps into a single set of equations. It'll be ugly and complex as hell of course, but there's nothing intrinsically wrong with it.

If you want a modern day example, consider rotating around a point not on the origin, which is a pretty common thing to do in geometry. To do so, you take your translation matrix T which "moves" the origin to the point you want to rotate around, then use the rotation matrix R to do the actual rotation, and then apply (T^-1) to "move" the origin back to where its supposed to be.

But thanks to the magic of matrix representation, you can create an new matrix M = T*R*(T^-1). If you apply M to any point, its exactly equivalent to doing the three individual operations (you'll have to go learn linear algebra if you don't believe me..)

Epicycles is exactly the same concept, except applied to planetary rotation. An epicycle equation E can be thought of as a translation T to the center of the sun, a measurement L for the location of the planet relative to the sun, and then a translation (T^-1) to "move" L back to Earth coordinates. All combined into a measurement M=T*L*(T^-1).

Ok I spent way too many words describing that.

Re:How sure are we...

[Livius]

That Mass is a real thing and not just a "theory"? Do we have any proof yet? I know there is almost no intel coming in on it, so it is easy to keep up with and/or follow.

I have an explanation

[slashmydots]

I think it doesn't interact with itself because it DOESN'T EXIST. It's a math error based on the arrogance that we can estimate all the mass in the entire universe.

Re:I have an explanation

[Anonymous Coward]

Oh, it's a simple math error? Then you can show us the error, right?

Maths and foundations of reasoning

[John Allsup]

Physics is built upon mathematical structures which have their origin in the 19th century.  Both Set Theory and Peano Arithmetic effectively grant you the assumption that there is no limit on how high you can effectively count.  This leads to models of these theories essentially asserting that there are countable numbers which are greater than the number of particles in the observable universe.  I fear this is leading to a hidden paradox in the reasoning process that physicists are using, albeit one that is hard to see and communicate.

Consider this assumption as follows:
(you can count) (higher than) (you can count)
and compare this with the statement 'X > X'. There must be a practical physical limit on counting, and by assuming this limit away, you are rendering the resulting reasoning system physically implausible. An effect known in classical logic is that from a single contradiction, using the rules of logic, you can logically derive any statement at all. The problem with the foundations of mathematics as they are is that they are incompatible with physical plausibility, and to naively shoehorrn in physical plausibility leads to logical inconsistency and 'weird stuff' appearing. I fear that this is the beast that theoretical physicists are actually wrestling with, albeit unknowingly.

Re:Maths and foundations of reasoning

[Anonymous Coward]

There may be a limit on things, but not counting. You could just count them all twice etc.

Re:Maths and foundations of reasoning

[Altrag]

At the risk of feeding a troll.. what the hell are you talking about?

Set theory indicates that the integers are infinite so therefore discovering new things in the universe that aren't covered by our known science is somehow nullified by edge cases in propositional logic?

You're not even discussing the same disciplines never mind making any sort of meaningful connection between your statements.

This leads to models of these theories essentially asserting that there are countable numbers which are greater than the number of particles in the observable universe.

So what? There are also countable numbers which are greater than the number of coffee mugs currently on my desk. What of it? I'm assuming you just don't understand what "countable" means in a mathematical sense.

There must be a practical physical limit on counting

Why? I mean if you started at one today and counted until you died, there would be a "practical physical limit" on how high you get based on your speed and lifespan. But what does that have to do with anything? I could perform the same "experiment" and reach a different number. Again, I'm assuming you don't know what "countable" actually means.

The problem with the foundations of mathematics as they are is that they are incompatible with physical plausibility

I.. don't even know where to start. What does "physical plausibility" even mean? The universe can do whatever the hell it wants. Its up to us to make our math fit the universe, not the other way around. If the math doesn't work we try to invent different math that does work. The universe continues not giving a shit and does whatever it wants as always.

Just for reference, not that I necessarily trust you'll understand it, but "countable" in a mathematical sense means "can be mapped to the set of natural numbers (aka positive integers.)" It says nothing about an upper limit to the size of the set and the mapping doesn't have to be in any way obvious. The full set of integers for example can be mapped as {0:1},{1:2},{-1:3},{2:4},{-2:5},... where the first value is one of the integer and the second is its mapping on to the natural numbers. Turns out the rational numbers (fractions) can be mapped with a bit of cleverness as well. The real numbers however cannot be, and therefore are uncountable.

But in no way does "countable" mean "do I have enough fingers/beans/particles in the universe." Those values are countable to be sure, but there are many countable sets that are far larger than those values, including infinitely countable sets such as the natural numbers themselves. You can start at one and keep incrementing by one at any speed you want and go until long past the heat death of the universe and still never find a point where you can say "I've done it! There is no next number!" But even with all of that, you still were just counting from one the same way you were taught in elementary school.

Of course there's no way to actually write a number that has more zeroes than there are particles in the universe but we've come up with notations to describe such numbers nonetheless. Consider the fact that you can't fully write out the decimal expansion of 1/3 either even if you used all of the particles in the universe for 3's and so we have to use the notation 1/3 to be accurate.

We just accept that because 1/3 is a number that has meaning at the human scale while 10^^^^75 is so far beyond our comprehension that its hard to imagine what it describes. But not being able to imagine it doesn't mean its not legitimate. It just means you aren't good enough at imagining things.

Can't help but look at this as particle physics

[Anonymous Coward]

If the gas (smallest particles involved) stops while the stars/planets (largest particles involved) keep going through eachother or bounce around imparting inertia one way or the other it seems reasonable to assume the gas would form new stars and planets and a smaller galaxy. It's like two atoms meeting and putting out a photon or similar over a cosmic timescale.

Dark Matter

[Z00L00K]

Dark Matter seems to me to be a placeholder item for differences between the calculated trajectories and real.

It do adjust for the effects observed but it does not explain what it really is.

Yeah, it's bit of a letdown.

[foreverdisillusioned]

I parsed the summary like this:

1. The gravity of dark matter affects luminous matter (we knew this.)

2. The gravity of dark matter doesn't affect other dark matter (...wtf?)

That would have been... interesting.

But I made the mistake of clicking the article and it looks like they're just talking about kinetic interactions (no observed slowdown due to "friction" between separately moving clouds.) I guess it's news, but given that we're already pretty sure it doesn't interact with baryonic matter (except through gravity) I'm not really shocked that it doesn't interact with itself either.

4th Dimension?

[Zorpheus]

I was wondering if dark matter could be matter in a 4 (or more)-dimensional space, so instead of coordinates x,y,z it is w,x,y,z. Ordinary matter is at w=0, while dark matter has some distance to ordinary matter in this 4th dimension. Adding a 4th dimension to gravity formulas is straightforward. We would feel the gravity of such matter on distances comparable to the w value of this matter.
If the dark matter's w value would become similar to ours it would suddenly appear in our 3-dimensional space. Since we never observed it the w value might be fixed. For example this could be galaxies in parallel universes. They would feel each others gravity and drag each other along with ech other, but otherwise they are invisible to each other.

Re:4th Dimension?

[Zorpheus]

And the dark matter of 2 galaxies could be other galaxies in different universes. They would only collide if they are in the same universe, or "plane" in the 4th dimension.

Re:4th Dimension?

[Zorpheus]

To make it more confusing, could that 4th dimension be the time? Meaning that a galaxy feels gravity from itself in earlier times.
Because of relativity this long-term gravitational effect has to move linearly with the objects through space, so it would kind of wobble with the galaxies when they moving relative to each other. When the galaxies collide the past gravitational effect would keep moving linearly.
Objects of all sizes would have this effect. But since planets moves around stars and stars don't move straight for long either the gravity can not build up over a long time, as it can on the scale of galaxies.

Re:4th Dimension?

[Altrag]

Yep. Entirely plausible. Even been considered by actual real scientists.

But since any testing of 4+ spatial dimensions is beyond our capabilities as 3 dimensional beings, those theories tend to get shelved as interesting mathematical models while we concentrate more on theories that may possibly lead to results eventually.

Of course if the alternate dimension theory is actually the right one, we may be spending a lot of time barking up the wrong tree.. but since we will never be able to tell if its the right theory (or which one is right if there's multiple alternate dimension theories,) deciding to accept it is basically equivalent to just giving up. And no real scientist wants to do that.

Re:4th Dimension?

[Anonymous Coward]

By definition, parallel universes are causally disconected. But don't feel bad, Stephen Hawkings has gotten away with peddling self contradicting bullshit for decades.

Premature theorising?

[Anonymous Coward]

These articles always make me ask whether physicists are perhaps jumping the gun slightly with theories about dark matter: perhaps better to accumulate more data before we put too many quick fixes into the theory? Then I realise that physicists are likely doing just that and I'm suffering from the distortion of looking at things through the lens of the press...

Re:Premature theorising?

[ledow]

I expect physicist to have thousands of hypotheses about dark matter.

Until you can design an experiment to distinguish between those that are bollocks and those that are true, you're not going to make any progress. That's the hard part - designing and performing such experiments. This is why beautiful and simple demonstrations like the double-slit experiments are considered the most artistic and wonderful pieces of science.

The problem with dark matter is that we have so little information about the phenomenon that all hypotheses fit and few can be eliminated.

Re:Premature theorising?

[Anonymous Coward]

You have to have a theory in effect really to push forward the data collection. Knowing what data to collect, where and why and how is based partly on existing theories. Theories are important in order to drive the subject forward and are essentially being tweaked non stop in light of the data as it comes flooding in. It is not quite as simple as just counting how many cars go past your house and then stopping to think about the mean number of cars per hour. This is oh so important for a subject like Dark Matter where, in effect, the theory arises purely out of not completely understanding why the experimental data didnt fit the existing theories.

Wrong Again

[Anonymous Coward]

It's turtles all the way down.

Occums Razor

[dbIII]

"It could mean our theories of gravitation are wrong" versus "there's something exerting gravity that we can't see any other way yet with our current instruments".
I know which head I'd put the fucking insulting "propeller beanie" on. Questioning is one thing, ridicule another.
Looks like you don't just despise climate scientists but all of them. What broken corner of society is turning out people spreading the drivel like this idiot's posting history? We need to prop it up with more jobs, better education funding or something to avoid drowning under a wave of destructive idiots.

Re:Occums Razor

[Karmashock]

Friend, I value empiricism. I am not a belief cultist... apparently you are.

You're also apparently a very petty person that likes to bring ad hominems into any discussion he possibly can. You are what is wrong with the internet.

If you valued the discussion more than your pathetic insults, perhaps you might have profitable discussions here... So far as I have seen, you don't. Not just with me. But with anyone.

I however have such discussions on this board all the time. Instead of disagreeing with me or offering up alternative opinions you have to devolve into this... pitiful.

Re:Occums Razor

[dbIII]

So it's OK for you to dish it out to the 'propellerheads", or climate scientists, or like you did to me earlier but it's not OK for it to be dished out in your direction when it's a criticism of your insults?
Pathetic.
Yet another reason we should find out what's wrong with your upbringing and make sure the next generation doesn't get subjected to the same mistakes.

Re:Occums Razor

[Karmashock]

My propeller beanie comment was directed at people that rejected the notion out of hand without even considering the issue.

As to other discussions, I'm not going to let you cloud this issue with your ad hominems against me.

You can either talk about the issue which is what I have always done... or you can go fuck yourself with a chain saw sideways.

Are you ABLE to have a discussion without falling into ad hominem or not?

Because when I throw out an insult, it isn't an ad hominem. I'm not saying "you're wrong because you're an idiot" I am saying "you are an idiot because you are wrong."

Pretty big difference from a logical stand point.

And for all my faults, I am logical.

From what I've seen of you lately, you have not been logical. You don't like to have discussions and you don't like to discuss issues. You just like to insult people, exclude people from discussions, dismiss people, throw out stupid insults, and generally troll.

So, you can either get on topic or go fuck yourself.

How about, shit for brains?

Re:Occums Razor

[dbIII]

My propeller beanie comment was directed at people that rejected the notion out of hand without even considering the issue.

Is that where you want to shift the goalposts? Then apply at least a grade school level of English and make it clear that a blanket insult is not meant to be a blanket insult when you make it then.
Poor little boy can dish it out but not take even a mild rebuke. How do we stop churning these entitled losers out?

Re:Occums Razor

[dbIII]

ad hominem

You STARTED with this one - that's what my post was about!

Here some someone with a propeller beanie on his head

So dishing it out but want to be immune from your own words being questioned. You've done it a LOT and seem to lurk here to do little more than push a luddite anti-science barrow.

M-Theory

[Anonymous Coward]

There is this Brane-Theorie based thing, that dark matter is actually the gravity that dark matter is acutally the gravity that leaks from other universes in our multiverse into our universe. That would explain the oberservation of the paper and why gravity is so weak compared to the other forces.

100 years from now...

[Anonymous Coward]

I have a feeling that this era will the called the "Dark Matter boondoggle" - where scientists went off in a completely wrong direction and our current level of science will be compared to how we think about the era where everyone believed the earth was the center of the universe and the sun revolved around it.

Silly Scientist...

I wish everyone would start dealing with what we know as facts (which seem to be very little).

I have a feeling that we won't be able to answer this question until we actually get "out there" and experience it ourselves (either virtually or physically).

Dark Matter: Can't see it, can't detect it, can't even prove it exists, can only observe it's effects: hmmm sounds like God to me. Please tell me the difference between the two...

rurz

[Anonymous Coward]

" dark matter is not only invisible to direct observation, it is invisible to itself!"

Sounds like impredicativity in their mathematical model to me! Poor physicists and their stubborn refusal to correct their logical errors! LOL!!!!

A couple of crackpot ideas

[Kevin Fishburne]

What if, like in OpenGL when you set the near and far clipping planes too far apart, you begin to lose precision on calculations at distances farthest away from the camera. The same thing happens at a certain point when you examine something near the camera too closely; you observe the limit of the floats describing the modelview matrix. This assumes of course that the universe is a simulation and that, being a part of the simulation, we "can't see the forest for all the trees". It might explain the discrepancy between the behavior of matter and energy at quantum scales versus galactic scales and why "normal" (as in Newtonian) physics seems to work perfectly at human scales.

Second, what if there are multiple dimensions affecting space/time/matter/energy/etc. and we and our observations are generally constrained to but a few. If dimensions were like pages in a book, sometimes the words on the next page faintly bleed into the one you're reading if the paper's thin. Perhaps these unexplained phenomena are the result of one or more other dimensions faintly bleeding over into the one we can reliably observe. Dark matter and dark energy could be the shadows of something larger that by our nature we're blind to. To further the craziness, singularities could be gateways that when in sufficient number make the effects observable at galactic scales.

Re:A couple of crackpot ideas

[Anonymous Coward]

So what you're saying is, the world is a simulation centered right around Sol, and we're suffering from IEEE 754 floating-point imprecision ?

I think KSP found a fix for that.

Re:A couple of crackpot ideas

[Kevin Fishburne]

So what you're saying is, the world is a simulation centered right around Sol, and we're suffering from IEEE 754 floating-point imprecision ?

I think KSP found a fix for that.

Well if it were a simulation, it wouldn't really have a center, just one or more "cameras" creating observable datasets. I suspect "they" would have a "camera" near anything sentient to keep them from completely freaking out. Maybe once a sentient being can prove they are in a simulation, as a reward for their cleverness their consciousness will be transplanted from the simulation to the "real world" where they will join the ranks of the "gods". No doubt pure bullshit, but it's fun to think of such things.

these ads suck

[Anonymous Coward]

The ads on this page take up too much space. I want t by email old slashdot back

Clinging to a hopeless theory?

[bradley13]

The lack of evidence for dark matter is becoming kind of embarrassing to the theory. Anything that should provide direct evidence doesn't - dark matter is seemingly only necessary to explain large-scale gravitational behavior, but is not otherwise in evidence.

For me, as a layman, dark matter was never persuasive: "there's this stuff that only has an effect way out there where we need it, but has no local effect where it would screw up our nice models". Sure there is. There are other theories that seem to be at least as reasonable. For example, what if the speed of light is not a constant across all time and space? This could dramatically change the behavior of the universe on large scales. I'm no cosmologist, but I understand that there are other theories as well.

In a double slit experiment the dark matter waves

[Anonymous Coward]

Dark matter has mass. Dark matter physically occupies three dimensional space. Dark matter is physically displaced by the particles of matter which exist in it and move through it.

The Milky Way's halo is not a clump of dark matter anchored to the Milky Way. The Milky Way is moving through and displacing the dark matter.

The Milky Way's halo is the state of displacement of the dark matter.

The Milky Way's halo is the deformation of spacetime.

What is referred to geometrically as the deformation of spacetime physically exists in nature as the state of displacement of the dark matter.

A moving particle has an associated dark matter displacement wave. In a double slit experiment the particle travels through a single slit and the associated wave in the dark matter passes through both.

Q. Why is the particle always detected traveling through a single slit in a double slit experiment?
A. The particle always travels through a single slit. It is the associated wave in the dark matter which passes through both.

What ripples when galaxy clusters collide is what waves in a double slit experiment; the dark matter.

Einstein's gravitational wave is de Broglie's wave of wave-particle duality; both are waves in the dark matter.

Dark matter displaced by matter relates general relativity and quantum mechanics.

Dark Matter and Dark Energy are non-existant

[hAckz0r]

They are both "Dark" because they do not exist. This article is a perfect case example of how Dark Matter would have to be distributed in a manor that generally ignores gravity itself. If it ignores the influence of gravity then how is it that its properties are defined by its influence on other objects through gravitational attraction? Do they really think that it can pull on things but ignore its own pull towards that non-dark matter?

Another stretchable theory

[Anonymous Coward]

How does dark energy/dark matter differ from luminiferous ether? Both explain difficult facts in a satisfying way. Both have no interaction other than whatever was needed for the theory to fit the facts