Mysterious Dark Matter Blob Confounds Experts

mayberry42 writes "Astronomers using the Hubble Space Telescope are mystified by a merging galaxy cluster known as Abell 520 in which concentrations of visible matter and dark matter have apparently come unglued. A report on the Hubble observations, published in the Astrophysical Journal, raises more questions than answers about a cosmic pile-up that's occurring 2.4 billion light-years away. 'According to our current theory,' says Arif Babul, the study team's senior theorist, 'galaxies and dark matter are expected to stay together, even through a collision. But that's not what's happening in Abell 520. Here, the dark matter appears to have pooled to form the dark core, but most of the associated galaxies seem to have moved on.'"

Comments

Re:Observed Dark Matter?

[Tablizer]

We can't directly observe air either (in most cases), but can still measure its effects.

Mysterious Dark Matter Blob Confounds Experts

[busyqth]

I'm pretty sure this headline is about my recent visit from the plumber.

Re:Mysterious Dark Matter Blob Confounds Experts

[vandamme]

It's Rush Limbaugh.

Move on

[oldhack]

The galaxies are gone. Horse has already left the barn. Spilled milk. Water under the bridge.

Dark matter needs to buck up, get it together, and move on, get on with the life. There is a whole universe out there.

Re:Move on

[snowgirl]

The galaxies are gone. Horse has already left the barn. Spilled milk. Water under the bridge.

No shit... best estimates are that this happened 2.4 billion years ago, so... yeah, grow up dark matter...

Re:Move on

[datavirtue]

The asgard chuckle....

Re:Move on

[Vaphell]

imo you can't really say 2.4 billion years ago. That would make sense only if there was one universal time scale with the necessary requirement of information being broadcasted instantaneously. Considering that it's not possible (hard cap of c), every point has its own time and events happen when information about them, spreading at the speed of light reaches said point. For us on Earth that dark matter stuff is happening right now.

Re:Move on

[snowgirl]

imo you can't really say 2.4 billion years ago. That would make sense only if there was one universal time scale with the necessary requirement of information being broadcasted instantaneously. Considering that it's not possible (hard cap of c), every point has its own time and events happen when information about them, spreading at the speed of light reaches said point. For us on Earth that dark matter stuff is happening right now.

Yeah, well, you're just speaking within your reference frame. In my reference frame, I'm located at a point equidistant in space and time from both this event, and you, and I see you responding to this event 2.4 billion years late...

Of course I won't actually see the light from you responding to this post until at the earliest 1.2 billion years from now... but since I can violate causality with my tachyon emissions, I've already witnessed your observation, and response, and responded myself....

All that aside, I was going to post that it happened "2.4 billions years away!" but I was afraid no one would get the joke...

Re:Move on

[drinkypoo]

No, they don't, but sometimes they give a really snarky blink and head-tilt.

Re:Observed Dark Matter?

[JoshuaZ]

We can't. What we can observe is the gravitational pull of dark matter (which is the entire reason we know it is there). In this case, they can see where the dark matter is because of its gravitational effects.

From my understanding...

[Zakabog]

From my understanding of dark matter, isn't it likely yhat they're looking at two entirely different types of matter? I thought dark matter was just matter that we can't "see" but can detect due to it's gravitational effect on visible light. So why would it be so far fetched to think there's more than one type of matter in the universe that we can't currently directly observe?

Re:From my understanding...

[Dunbal]

isn't it likely yhat they're looking at two entirely different types of matter?

Yup, typical response from physicists for oh I dunno almost the past 100 years. Can't explain something? Must be a new particle...

Re:From my understanding...

[Anonymous Coward]

You say that like it's a bad thing. Or a wrong thing. There's a lot of people who seem to think that Science is something for settling very large issues, so that when it is wrong, it is very very wrong: believing that red things are actually green, or something like that. This is almost never the case: Science is the search for the least wrong understanding of the universe, and for the most part we understand the universe well. In this case, the alternative theories suck. In particle physics, we have scientists spending years to confirm whether particles actually exist. What is your basis to contradict that?

to GP, dark matter is yes, a fundamentally different type of matter, in theory. It is expected to be non-baryonic, that is, not made of quarks (electrons are also composed of different particles). Is it a law that the people who are most skeptical are the most ignorant, or just a six sigma correlation?

Re:From my understanding...

[Baloroth]

No, that isn't far fetched at all, and it is entirely possible (maybe even likely). However, the philosophical principles that guide science dictate that we should reduce effects to the fewest possible number of causes. If two causes suffice to explain the phenomenon, one should not introduce a third. You can introduce new principles/causes/etc ad infinitum, but unless they are required to explain the observations, they are more or less worthless. In other words, one should postulate only as many kinds of matter as have been observed (but not that there are definitely only those kinds).

Re:From my understanding...

[Livius]

No, you're thinking of the scriptwriters of Star Trek Voyager.

Re:From my understanding...

[Rich0]

There are other possible ways that the same phenomena could lead to different outcomes. How about this one - galaxies/clusters are composed of stars and hot gas, and that's it - there is no dark matter. However, we exist in a multiverse with many parallel universes overlaying ours but interacting only through gravity. Since matter in different universes attracts each other, galaxies in one universe tend to be piled on top of galaxies in other universes. Much of the mass of any cluster/galaxy is in the hot gas.

Now, let's take the bullet cluster. Let's explain that by the collision of 4 clusters in three universes. Universe A is ours, and B and C are others that are close by and interact gravitationally. Two of the clusters are in A (call them 1 and 2), one is in B (call it 3), and one is in C (call it 4). 1 and 3 overlap, and 2 and 4 overlap. When they cross paths, the hot gas in 1 and 2 interact via electromagnetism, and the hot gas in 3 and 4 only interact gravitationally and aren't slowed down as much. In the end the gas in our universe in clusters 1 and 2 ends up in the middle, and the gas in 3 and 4 are visible as dark matter on the outside.

As the second example let's consider this collision. Let's explain that using 4 clusters in two universes, again with A being ours and B being another one. Clusters 1 and 2 are in ours, and 3 and 4 are in B. 1 and 3 overlap, as do 2 and 4. In this scenario the hot gasses in 1 and 2 interact, and so do the hot gases in 3 and 4. That means that the hot gases all end up in the middle in all 4, and the stars all fly past each other and end up on the outside. So, this time we see hot gas in the middle, plus a lot of dark matter, which is all the hot gas in 3 and 4.

So, we can have "dark matter" behaving in two different ways, not because of any difference in the matter itself, but rather a difference in the space in which it exists.

No doubt somebody much smarter than me has thought up something like this already, and perhaps shot it full of holes as well.

Re:From my understanding...

[ChromaticDragon]

Nothing likely wrong about positing multiple types of dark matter...

But what I think is really bothering folk about the supposed contradiction here is why would one galaxy or galaxy cluster have one type and another galaxy or galaxy cluster have another? This in and of itself would seem to be a rather flagrant violation of the Mediocrity Principle.

It would seem more likely that both galaxies would have a blend, if you will.

Is there a time component here? Would dark matter be different in one epoch vs. another? Does it evolve or change over time? The Bullet Cluster is 150 million years back. This new set is a couple billion years back. On the face of it, that'd be just another violation of the Mediocrity Principle, just in time rather than space. But who knows...

Re:From my understanding...

[osu-neko]

Yup, typical response from physicists for oh I dunno almost the past 100 years. Can't explain something? Must be a new particle...

Yup. Can't explain something, but it would be explained if a certain particle with such and such properties exist, let's go look for it... and lo, there it is! It's amazing what you can discover if you're willing do more than just throw up your hands and say, "hmm, can't explain that."

Re:From my understanding...

[Raenex]

From my understanding of dark matter, isn't it likely yhat they're looking at two entirely different types of matter?

This was one of the possibilities (the third one below) raised in the article:

"Jee, Babul and their colleagues propose several possible explanations for the discrepancy. One explanation might be that the dynamics of the Abell 520 collision are more complex than the Bullet Cluster's crash. Maybe multiple collisions, involving three or four galaxy clusters, have led to the dark matter pile-up.

Another possibility is that there's actually lots of ordinary galactic material in the core, but it's just too dim to be seen, even by Hubble. That would suggest that the super-dim galaxies in the core have somehow formed far fewer stars than normal galaxies.

The most unsettling scenario proposes that there are different kinds of dark matter, and some of those kinds are "stickier" than others. Abell 520 might have a particularly sticky kind of dark matter that interacts with itself and clumps up like a wet snowball."

Re:From my understanding...

[Raenex]

But what I think is really bothering folk about the supposed contradiction here is why would one galaxy or galaxy cluster have one type and another galaxy or galaxy cluster have another? This in and of itself would seem to be a rather flagrant violation of the Mediocrity Principle.

Not necessarily. Galaxies come in many different types:

http://en.wikipedia.org/wiki/Galaxy#Types_and_morphology

Re:From my understanding...

[BiggerIsBetter]

Interesting theory and similar to things I've wondered about too. It might one of those theories that's very difficult to prove either way.

Re:From my understanding...

[Anonymous Coward]

Out of interest, do you seriously believe that "dark matter" is *actually* one type of particle?

Look at it this way. On the one hand, we have 5% of the universe (and about 20% of the matter content) is the standard model, which to our current knowledge contains three flavours of quark and three flavours of leptons at a fundamental level and an absolute menagerie of combinations of these. Why do people - and I most definitely include professionals in this - seem to think that if 5% of the universe can be described by an equation that can be written on a piece of A4 and six particles (along with four or five gauge bosons), 25% of it is described by.... dark matter. Which is apparently one type of particle, described by one equation: w=0. That's frankly not believable.

I can answer my own question, by the way: people believe this because we can't actually parameterise a better model. If you can't distinguish between two models, they're more or less meaningless. When more data comes in, *then* you can think of things more complicated. And at that point I think a lot of people will face reality: dark matter is very likely a mixture of modifications to gravity, the lightest supersymmetric particle (let's say a neutralino), some other particles currently not thought of, massive neutrinos, poor applications of gravitational physics, and Lord alone knows what else.

Re:From my understanding...

[maxwell demon]

(electrons are also composed of different particles)

According to our current understanding, electrons are not assembled at all.

Re:From my understanding...

[boristhespider]

What you're talking about is very similar to the effects of braneworld theories, where our universe is living on a 3D brane to which we're confined. There are, of course, other branes hanging around in the wonderful 11D multiverse. In M theory, gravitons are closed strings and can float freely between the branes, while photons (and, indeed, the rest of the standard model particles) are open strings whose ends are confined to a brane. (Note that saying "In M theory" is itself a bit dubious since M theory doesn't really exist, but let's pass over that for a minute.) That means that if two branes pass close to one another, technically galactic clusters on each brane can interact gravitationally, but cannot interact electromagnetically.

Demonstrating much of this properly is, of course, another issue. We don't possess M theory, so we can't solve the system. The best we've done so far is make lower dimensional braneworlds - such as 3+1D branes hanging in a 4+1D universe - and see the effects. And there are some - effective masses for gravitons is one. Less pleasingly, you also have myriad causality issues what with, say, gravitons propagating off one brane and scattering off particles on another brane. If the branes are distorted in the right kind of configuration, an observer on the first brane will see a graviton propagating arbitrarily faster than light.

Then again, all this is basically results found from studying a toy model that people hope will in some way resemble an actual configuration from M theory. The reality may be very different. (And, of course, the reality may bear no resemblence to M theory at all, and may even be that we live in a 3+1D universe the way we've always thought.)

Re:From my understanding...

[drinkypoo]

Has anyone seen an anti-photon yet?

Re:From my understanding...

[flyneye]

Wow, you again, trolling for karma discipline in a suicidal way in the midst of so many physics nerds.

Girlfriend, dumped you?
Buck up little buddy, there are plenty of theorys to cover gravity. I will pull an obscure rabbit out of my ass for you.
Have an understanding of electromagnetic theory. Think of it as a prerequisite to the mysteries of physics in this arena as opposed to the quantum mechanics in the garage over there. We haven't unified the dept.s yet.
Now although, for instance, our Earth core is mostly Ni and subject to being the most magnetic thing we have on hand,we currently do not consider gravity to be the product/byproduct of gravity within massive bodies.
BUT, if we take into consideration other predicted dimensions outside our 3 we can start to see dark matter as being trace evidence in the form of aftermath of a bisection of dimensions from forces perhaps related to "Bango Grande' ". As far as energy potential goes, that would be a good starting point.The spew from the theoretical bungholes of black holes could give us some insight if only we could stick our heads up there like we do here.Perhaps this would explain this strange state of dark matter. We can see gravity being resultant of interaction of magnetism being acted upon, tied to or resultant of cross dimensional current. This may also explain seeing one galactic crash collecting and the other repelling + and -. Not magnetism but a similar force from interaction related to our theoretical,now more probable additional dimensions . Now, just to refresh your feeling of "you are here " on the map. Height, we can have points A and B. Height and Width, cool now we can have a flat dimension to add C, but it is no more anticipated by our 1 dimension than our flat dimension inhabitants can see the third dimension with depth and we in our 3 dimensions can only scribble out our thoughts on 4 and beyond. Perhaps we can think of Dark matter and gravity as dimension 3.5. Let's string a soup-can phone over to the mechanics in the quantum garage and invite them to a pub crawl on the unified party(cle) bus.

Now if you tell the blonde that one after a coupla rum drinks, you got it made. I'd leave off the bit about dark holes and bung holes though.

Re:From my understanding...

[mbone]

The way I prefer to state this is that "Dark Matter" is a sign that there is something we don't know about the physics of large scale matter. We know that there is missing physics, but we don't know where it is. If it is in some new "Cold Dark Matter," (or CDM) the missing physics is in quantum field theory. If, as in Milgrom's MOND hypothesis, the problem is with gravity on large scales or weak accelerations, the missing physics is in gravitation. Your idea would put the missing physics in extra-dimensions, i.e., brane theory, which I regard as perfectly plausible. The point is, we don't know. All we really do know is that there is a hole in the system. We call that hole "Dark Matter," but at present there is no proof that this is necessarily due to non-interacting particles (i.e., CDM).

Note that this can get tricky. Dark Matter cannot be baryons (i.e., normal matter, like us) because that would violate various constraints from nucleosynthesis. However, there may be some missing baryonic matter, so in some cases evidence for dark matter may not _require_ Dark Matter or CDM. Also, if you are going to explain Dark Matter as some new gravitational type field, that may also require new particles, and so may have a CDM type analogue. And, of course, if you are mucking around with field theories you may conceivably change the nucleosynthesis constraints.

Now, in cases such as this (specifically the original case, the Bullet Cluster), there have been claims that the separation of Dark Matter and visible matter invalidates MOND. Milgrom disagrees.

My personal feeling is that we are too distant and, even more importantly, have much too short an observational history, to be able to do pure physics with galaxy clusters, and that a proof or disproof of CDM or MOND or brane theory will have to come elsewhere, in the lab, in solar system observations, or through observations of gravitational waves. (CDM would have the normal gravitational waves of General Relativity, while the relativistic version of MOND, TeVeS, would not. Brane theories predict different deflection / delay of light due to matter than General Relativity. Both can be tested here, in the solar system.)

Re:From my understanding...

[John Hasler]

Photons are their own anti-particles.

Re:From my understanding...

[Fastolfe]

Yes, it's called a "photon".

Re:From my understanding...

[drinkypoo]

Nobody has even seen the first photon, we only can measure its intersection with something. Pretty sure nobody has seen the antiphoton that mediates the exchange of energy, either, but maybe you've got some magical specs from the back of a comic book that let you do that.

Since we still don't know what photons actually do in between the time they're emitted and the time we can observe them, we've just got a working model that lets us predict where the photon will be, then really it could all be working very differently from all this particle physics stuff, and it only seems this way because of the way we're restricted to looking at it. Which, I gather, is the whole concept behind the string idea.

Re:From my understanding...

[lewiscr]

The Galactic Rotational Velocity implies that dark matter is something different than standard matter, not just invisible matter. I'm broadly covering all forms of invisible matter here, cold-dark matter, non-baryonic matter, matter in other branes, etc.

Using your idea with the galactic rotational curve, the thought exercise would not yield the required mass distribution to explain the rotational curve.

Now, if we posit that nearby branes don't necessarily have the exact same physical constants, that could result in brane-sibling galaxies having different shapes depending on the local physics. While interesting, we're well into the realms of science fiction.

In short, I like you idea, and need to think about it some more.

Re:From my understanding...

[Rich0]

Good point - just dumping a second galaxy on top of our own in some other universe would put too much mass in the center. Maybe as you suggest if constants were different it would be more sparse and we'd have more mass outside.

If you allow for a much larger number of nearby branes then maybe gas that is gravitationally coupled to the galaxy might work. Gas might fall from voids and tend to orbit a galaxy in our universe, but since it doesn't interact non-gravitationally it wouldn't clump as much near the center. Of course, that requires the gas to be spread across many different universes, or it would still clump up. Then, if there is so much background mass all over the place that can't clump up, then would that tend to prevent galaxies from forming in the first place? I don't really know enough about the dark matter problem to answer that offhand...

Re:From my understanding...

[lewiscr]

Sorry for the fast thinking here. I'd written a much longer post, but /. ate it when I tried to login.

What is the psuedo-distance between branes?

We know that gravity's effects drop of as distance^2. Working under the theory that gravity propigates at the speed of light, we can measure brane distance in light seconds. If branes are only a light-second away, there's too much mass. Too many branes too close together would turn everything into a black hole.

If we assume some non-trivial distance between branes, say 1000 light years, then that could explain the distribution of regular vs. dark matter. I don't feel like integrating galactic masses over distance^2 right now, but the ratio of regular vs. dark matter should be able to tell us how far apart branes are.

Rolling with 1000 light years (an order of magnitude doesn't affect this thought experiment). Larger structures (galaxies, clusters, etc) would be gravitationaly bound cross-brane, but smaller structures (stars) would not.

That's enough n-dimensional physics for me tonight.

Re:Observed Dark Matter?

[muecksteiner]

Right, except that we are talking about fairly static images of (for all practical purposes, randomly placed) stars and galaxies billions of light years away. How exactly does one figure out gravitational effects between the stars and galaxies in such an image?

Re:Observed Dark Matter?

[KingBenny]

maybe it's just those rogue neutrino's acting pranks again

Barricade your basement doors!!!!!

[rts008]

I've seen this before.

We are all DOOMED!

tribbles!

[Anonymous Coward]

Must be a cosmic pile-up of tribbles.

Re:tribbles!

[AbRASiON]

Sounds like we need one of those incredibly dangerous tribble harvesters.
http://419eater.com/html/tope.htm

(worth reading)

Re:Observed Dark Matter?

[Ruie]

One way to figure out gravitational field from a static image is to look at galaxy distribution behind the gravitational field. If it is squishes space in one direction while stretching it in the other, you will see more galaxies longer in one direction then in the other, so you can build a map of distortion and compute gravitational field from it. The result will be coarse, but you will see large concentrations of matter.

Re:Observed Dark Matter?

[JoshuaZ]

They detected it by gravitational lensing. http://en.wikipedia.org/wiki/Gravitational_lens. The dark matter is massive enough that it bends the light passing through it. So you can for example see that a star looks bent and not as spherical if it is behind a lot of dark matter. In the really blatant examples of gravitational lensing you get things like the Einstein Cross http://en.wikipedia.org/wiki/Einstein_Cross where you can see multiple copies of the same object.

Awoken

[roman_mir]

Awoken the Grue has been.

Oddly enough, The Fifth Element is on right now

[GodfatherofSoul]

Make sure to call me if that blob starts moving towards earth!

Re:Observed Dark Matter?

[History's Coming To]

In some cases the red shift can give you velocity information from a "snapshot", nature's good with compression algorithms ;)
Not sure if there's enough variation in this case to make it particularly useful, I'll probably have to read the fine article.

Dark MAtter theory now falsifiable?

[RichyRoo]

If Abell 520 has had the DM 'stripped from its galaxies' (from the link) and since DM was originally postulated to explain the difference between theoretical and observed rotation rates of the core and periphery of galaxies... shouldnt the galaxies of Abell 520, stipped of their DM, now be rotating in accordance with the original theory? That is to say, if gravitational theory predicts that, sans DM, the cores of galaxies will rotate more quicky than the periphery, and these galaxies are now 'sans DM', wouldnt that open the opportunity to provide falsification or support to the DM hypothesis by checking if the galaxies of Abell 520 are indeed rotating differently now that the DM has been removed?

Re:Dark MAtter theory now falsifiable?

[l0ungeb0y]

Care to tell us how they were rotating previously?

Re:Dark MAtter theory now falsifiable?

[RichyRoo]

In theory the cores of galaxies should be rotating faster than the periphery, however observation contradicts this. So the hypothesis was postulated that there was additional 'dark' matter surrounding galaxies which could cause the periphery to rotate faster. If Abell 520 has had its dark matter removed, its periphery should be rotating in accordance with standard gravitational theory, rather than as effected by invisible dark matter. Its pretty simple really.

Re:Dark MAtter theory now falsifiable?

[osu-neko]

Yes... and in a few million years, we can compare it to the images we took today and see if that's the case...

Re:Dark MAtter theory now falsifiable?

[mbone]

In theory the cores of galaxies should be rotating faster than the periphery, however observation contradicts this. So the hypothesis was postulated that there was additional 'dark' matter surrounding galaxies which could cause the periphery to rotate faster.
If Abell 520 has had its dark matter removed, its periphery should be rotating in accordance with standard gravitational theory, rather than as effected by invisible dark matter. Its pretty simple really.

Falsifiable ? Yes, but probably not this way. First off, A520 is a cluster of galaxies, not a single one. The dark matter orbiting the galaxy core is going to be tightly bound to that galaxy, and won't be stripped by a cluster collision. And (see my post below), anyway it's not the stars, but the gas that gets separated from the dark matter.

Re:Dark MAtter theory now falsifiable?

[maxwell demon]

Ever heard of the Doppler effect?

Re:Dark MAtter theory now falsifiable?

[justthinkit]

I don't understand why stars should rotate as planets do. In our system there are 8 small (relative to the sun) planets scattered across several billion miles. In a galaxy there are 100 billion stars rotating -- so wouldn't the gravitational effect of one star on the next be substantial? In the extreme density case of a rotating solid object, all parts of the object rotate at the same speed. Aren't a galaxy's stars "more solid" than our solar system's planets?

Its simple

[fyngyrz]

Here, the dark matter appears to have pooled to form the dark core, but most of the associated galaxies seem to have moved on.

When we get to look more closely, we'll see it's a convention of elephants and tortoises.

Re:Its simple

[rust627]

four elephants, standing on the back of a great space turtle ........

Re:Its simple

[flyneye]

One elephant holding a clover with a dustspeck ......

Re:Observed Dark Matter?

[PopeRatzo]

Seriously? That's how they do it?

That is so cool. Is this something that would be detectible by a person looking at one of these images or is the effect too subtle? I'd love to look at some of those images, if it was an effect I could see.

Do you think any of these images are available? I tried googling but none of the combinations of terms gave me anything I could look at.

Must I explain everything????

[sgt_doom]

Obviously, the Death Star detritus, along with the burntout hulks of various starships blown out of existence by Luke and Hans and that furr-faced fellow, had to congregate someplace........

Re:Must I explain everything????

[mbone]

Wasn't it standard Imperial procedure to jettison their garbage there ?

Re:Observed Dark Matter?

[Ruie]

Here is general description and large annotated Hubble image

Throw out the existing theories

[grantspassalan]

The theories existing now are obviously wrong. Scientists, especially cosmologist these days are always puzzled, perplexed, surprised, mystified and confounded by the unexpected data that does not fit into any of their theories. There are theories that other people have come up with that don't require dark matter, dark energy, black holes and other convoluted mathematical constructs that have never been observed in real life. Maybe it is time to throw out the old theories and consider some of these theories, which up till now have been dismissed as crackpot ideas. Maybe some of those alternate theories that have been labeled “crackpot” need to be looked at more seriously in light of the flood of data confounding, perplexing and fooling current mainstream scientists.

Re:Throw out the existing theories

[Daniel Dvorkin]

Maybe some of those alternate theories that have been labeled âoecrackpotâ need to be looked at more seriously in light of the flood of data confounding, perplexing and fooling current mainstream scientists.

Maybe the crackpots should present some real evidence instead of acting so much like, well, crackpots. Specifically, maybe they should submit their work for publication and stop posting their "results" on web sites full of eye-bleeding color schemes, pretty Hubble pictures (which are, BTW, published by those evil "mainstream" scientists) that have nothing do to with the issues at hand, accusations of censorship and suppression by The Scientific Establishment, and "refutations" of existing theories that all pretty much boil down to "nuh-uh!"

Re:Throw out the existing theories

[bmo]

The thing is that the people who are /always/ wrong are the ones who are cocksure, such as yourself.

When you change the model to fit the data, we call that science.

Everything else is snake oil, religion, and dogma.

--
BMO

Re:Throw out the existing theories

[Raenex]

Scientists don't just "throw out" theories if they can be patched and no solid alternative exists. They do, however, look at plausible alternatives:

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

Dark matter is just the prevailing theory. Working scientists know that it might be wrong and the equations for gravity may have to be fixed.

Re:Throw out the existing theories

[osu-neko]

There are theories that other people have come up with that don't require dark matter...

These theories are even more at odds with the observed effects here than our current theories. What we're seeing in this case is dark matter behaving in an unexpected manner. A theory that posits dark matter doesn't even exist would have a much, much harder time explaining its observed behavior...

Re:Throw out the existing theories

[osu-neko]

BTW, what you're suggesting here is the equivalent of saying, "oh look, the Earth's magnetic pole isn't moving exactly the way our theory predicts -- we should toss out this crackpot theory that the Earth is round."

Re:Throw out the existing theories

[grantspassalan]

Many scientific theories held by the majority, sometimes for centuries, were overthrown by observant people working alone. Some of these were never vindicated by majority scientists until many years after these lonesome scientists died. There are many examples of this. I will just give one.

For centuries it was the consensus among scientists, that the speed of light was instantaneous, that is it took no time at all to travel any distance. There were even “experiments” done with lanterns and shutters on mountain tops to “prove” this scientific “fact”. Then in 1611 A Danish astronomer, carefully observing the Jovian moon Io, noticed that the appearance of it's eclipses were not what they should be according to orbital mechanics. He calculated the speed of light amazingly close to what we know it to be today. However it took another 150 years, before technology advanced enough, to enable countless experiments to finally overturn the stubborn commonly held scientific beliefs of the majority. There are other examples of this sort of thing throughout the history of science.

Re:Throw out the existing theories

[maxwell demon]

Many scientific theories held by the majority, sometimes for centuries, were overthrown by observant people working alone.

But unlike the typical crackpot, they understood the theories they overthrew. And they replaced them with better theories, not with ideas which already had been shown to be wrong long ago. And they didn't have to deny experimental results either, nor claim some conspiracy against their ideas.

Re:Throw out the existing theories

[Black Parrot]

Many scientific theories held by the majority, sometimes for centuries, were overthrown by observant people working alone.

Alas, Bozo the Clown worked alone too.

Re:Throw out the existing theories

[Black Parrot]

When you change the model to fit the data, we call that science.

And when you change the data to fit the model, we call that marketing.

Re:Throw out the existing theories

[grantspassalan]

Yes, but Bozo the clown did not come up with any workable new scientific theories, that eventually overthrew widely held scientific dogmas.

Re:Observed Dark Matter?

[Smauler]

We can't directly observe air either (in most cases), but can still measure its effects.

What? Seriously, what?

The human body has plenty of senses, a lot of which detect air directly. Touch would be the first simple example. To be honest, I'm having a hard time thinking of a sense that doesn't experience air - all would be affected..

Pressure chamber

[drerwk]

If it gets you you'd best jump into a pressure chamber, it's you only hope.

Re:Not to be pedantic, but

[Daniel Dvorkin]

It's pretty conventional, when discussing astronomical observations, to use the present tense for "when we see it." Since it can't possibly have any effect on us before the light from the event gets here (assuming relativity is correct, yadda yadda) this makes sense. Also, having to say "2.4 billion years ago 2.4 billion light-years away" would just get annoyingly redundant after a while.

There's pedantry which serves the useful purpose of correcting other people's mistakes, and then there's pedantry of the "look how clever I am" variety; posts like yours, which seem to get posted to every single story on any kind of astronomical event that takes place outside the solar system, are examples of the latter.

Don't feel bad

[wbr1]

Mysterious Dark Matter Blob Confounds Experts

My ex-wife confounds me too.

Re:Don't feel bad

[datavirtue]

Is this where people come after they get divorced? Cool!

Re:Observed Dark Matter?

[ThePeices]

Hi there,

You seem to have missed reading the word 'observed' in your reply to the poster above. You cannot see air, you cannot see dark matter. Directly. (dark matter does not interact with matter via the Electromagnetic Force). But through measuring its other effects on matter, we can infer its existence. Kind of like air. (please note the use of the word 'kind' in the previous sentence)

The poster above was making the point that we cannot see air through the visible spectrum that our eyes detect. He made this point to show the similarity to how we can detect ( but cannot see ), dark matter.

That is the reason you could not make sense of his post. Now that the word 'observed' has been pointed out to you, everything will now become clear to you.

Experts Confounded

[ThePeices]

I see the experts were Confounded.

Does anybody know if they were also Baffled, or Stumped? It would also be good to know if they were also left Scratching Their Heads?

Oh yeah, were they Dumbfounded too?

Re:Experts Confounded

[bmo]

"The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt." -- Bertrand Russell

And you have proved which one you are.

--
BMO

The Default

[rust627]

The default position for scientists is "I don't know"
everything else is trying to define and explain
this is why nothing is set as a certainty but always as a theory
a Theory (theory of gravity, theory of climate change etc.) is usually the best most simple hypothesis that explains experimentally verifiable data.
you can create any theory you want from the incredibly convoluted to the overly simplistic (because god made it so strikes me as an overly simplistic theorem).
Usually the simplest (but not most simplistic) theory will be the one that gains the most credence in the scientific community.
the KISS rule applies very much in science too.

Re:Not to be pedantic, but

[bmo]

There's pedantry which serves the useful purpose of correcting other people's mistakes, and then there's pedantry of the "look how clever I am" variety; posts like yours, which seem to get posted to every single story on any kind of astronomical event that takes place outside the solar system, are examples of the latter.

There is an excellent word for this and it means far more than just "pedant" and it's Finnish.

The word is pilkunnussija, literally "comma fucker"

The more you know.

--
BMO - perkele

Cold sweat

[flyingfsck]

It must be cold sweat left behind by two fighting galaxies.

Re:Not to be pedantic, but

[Daniel Dvorkin]

Oh, that's brilliant!

Re:What happens if it turns out that dark matter i

[PPH]

God?

We'll have to revise the Sistene Chapel ceiling, for one thing.

Matter drag

[mbone]

This should not be too confounding. Suppose you have two galaxies collide. The dark matter will sail right through the other galaxy, affected only by the overall gravity. The stars will almost never hit each other, so the vast majority of them will be affected only by the overall gravity too. The gas and dust will not - dust is subject to radiation pressure, and gas (plasma) magnetic fields. Once the gas and the dark matter become separated, there is no guarantee they will ever get back together. As the paper says :

One of the key tools for studying merging clusters is the comparison among the distributions of the three cluster constituents: galaxies, hot plasma, and dark matter. For example, in merging clusters the intracluster medium suffers from ram pressure and lags behind galaxies and dark matter, which are believed to be effectively collisionless. The contrast between collisional and collisionless components becomes highest when we observe merging clusters at their core pass-through, when both the medium velocity and the effect of ram pressure stripping are largest.

Re:Not to be pedantic, but

[osu-neko]

FTS: A report...published in the Astrophysical Journal, raises more questions than answers about a cosmic pile-up that's occurring 2.4 billion light-years away.

Should that be "occured 2.4 billion years ago"?

To be perfectly pedantic, it should be "that occurred 2.4 billion years away". Your "correction" is making an entirely different statement, which although true, is not what the original was saying.

Oh wow

[identity0]

>2012
>Still using Hubble
>Costanza_smirking.jpg

In all seriousness, I am impressed this thing is still working. I would have thought it was retired by now. Way to go, Nasa!

Re:Oh wow

[mbone]

It is still working because it was serviceable, and was serviced. (It is no longer scheduled to be, so it won't last too much longer.) That is a rare thing at NASA, which tends to be dominated by people who would rather spend money building things.

Dumped useless ballast

[korpique]

It dragged them down unnecessarily and nobody figured any way to use it for anything so they schemed a plot to leave it behind.

Re:Observed Dark Matter?

[Anonymous Coward]

observing refraction of light into air != observing air.

slight difference

[slashmydots]

They call it dark matter but I call it a mathematical error. That makes the whole situation make A LOT more sense than made-up physics of made up materials actually.

Re:Observed Dark Matter?

[hughJ]

http://www.youtube.com/watch?v=7ImvlS8PLIo#t=1582s Worth watching the whole thing, but this portion briefly addresses gravitational lensing.

Re:Observed Dark Matter?

[Man Eating Duck]

It is obvious that we are toddlers when it comes to understanding cosmic forces. When we can manipulate gravity to our will I will then listen to what these crackpots theorize about black holes, dark matter, and generally any other phenomena we can't OBSERVE.

Probably feeding a troll here, but... seriously, what the fuck are you going on about? Sure, you just lean back and wait until we can "manipulate gravity to our will" (don't hold your breath), meanwhile the rest of us will continue trying to figure this out. Mind you, "figuring this out" is a likely prerequisite for your goal.

Re:Observed Dark Matter? roxy

[hughJ]

"Dark matter" isn't simply regular matter/particles that we just can't see due to not emitting light. We may not know quite what it is, but we have a pretty good idea about what it is not, and that's regular matter as we know it.

Re:Observed Dark Matter?

[robbiedo]

Apparently, you never lived in Los Angeles.

Re:Observed Dark Matter?

[maxwell demon]

If people had done that throughout history, our current understanding of the world would not be much different from that in the stone age. You'd have no computer and no internet, no electricity, no steam engine, not even windmills. Every advance in human knowledge comes from looking for explanations. Some explanations later turn out to be wrong, those are then thrown away. Other explanations turn out to stand the test of time. The latter make up our knowledge about the universe.

Re:Why are we even studying

[maxwell demon]

We are also still studying dinosaurs. Just saying.

Also, the aliens watching the dinosaur earth might learn about the important of defending against asteroids.

Re:Observed Dark Matter?

[Anonymous Coward]

Hi there,

You seem to have missed reading the word 'observed' in your reply to the poster above. You cannot see air, you cannot see dark matter.

You live in a bubble of inexperience so explaining this to you might be like explaining the concept of colour to a blind man.
You beleive that air can't be seen because you can't consider what "not air" is. Try to dive underwater and open you eyes, compare to what it looks like above the surface. Try looking through a window, now open the window and look at the world without it. Now consider the difference between looking at the sky without air inbetween and with air inbetween. (Pro-tip; the sky wouldn't be blue if it weren't for the air.)

Now, the thing with dark matter is that there is no real evidence for it's existence, it's just that unless we point at it and say "there has to be matter here" our current models for explaining the universe falls apart.
The problem is that dark matter by itself does not fit with our models since it doesn't interact with other particles iin a way that is supported.
Basically dark matter is a patch that allows us to say "there is nothing wrong, the world is flat".

Re:What happens if it turns out that dark matter i

[Black Parrot]

God?

Seems to fit:
- provides structure
- omnipresent

- never seen them both at the same party

I think you're onto something! (Or maybe just on something?)

Re:Antimatter

[Black Parrot]

Antimatter caused the visible/dark matter to come unglued.

But is anti-darkmatter the same thing as dark-antimatter?

Re:Observed Dark Matter?

[flyneye]

Specifically according to video documents held by Warner Brothers Communications filmed by the Acme Corp. " The world, she'sa flat like-a you head" presented as the counterpoint to Christopher Columbus' posit that "The world, she'sa round like-a you head" which brought about a realtime demonstration of the plane of an Acme frying pan forming the concept of flat on Columbus' head followed by the quote in question.
Sorry, feeling pedantic today.

Re:Observed Dark Matter?

[Intrepid imaginaut]

It is cool, and consider the implications for future space propulsion utilising something that only interacts gravitationally with this universe... :D

Re:Observed Dark Matter?

[flyneye]

Uncertainty, Quantum conflicts, quagmires of rejected theorems that may live again due to new data?

Re:Observed Dark Matter?

[flyneye]

Pardon, but I think I can clear away your fog of confusion and I don't really think you deserve flamebait mod for your special feelings. Please, at least ,someone give him underrated.

        I can see by your 7 digit slashdot u.i.d. that statistically you may be a younger man with less experience, so no one should fault you.
From the relative standpoint of ; for a "fucks" sake, you would never say" I don't know" , which would result in not impressing a potential if not tipsy partner for a mating ritual. Honestly, Sheldon, just read the book we got you ...

Correlation =/= Causation?

[MassiveForces]

Could it be that the universe's entire playing field is just stuffed with warped areas here and there for no reason other than that there's no reason it should be smooth either, and galaxies form and move around these areas? I suppose if those underlying distortions themselves can move around then whether it's a form of matter or not might be moot. Any astrophysicists care to explain?

Re:Why are we even studying

[mbone]

Likewise, an alien species looking at Earth is probably seeing a bunch of dinosaurs, and we all know how THAT turned out.

Actually, we don't. The birds may outlast us yet.

Re:What happens if it turns out that dark matter i

[mbone]

So God is universal, omnipresent, and doesn't interact directly with people at all.

Sounds like the Unitarian-Universalists were right !

Re:Not to be pedantic, but

[dwye]

Is the Finnish pilkunnussija different from the netnews-era English-writing term grammar nazi?

Anyway, the correct response to shotgun's original question is that the two formulations are equivalent in this case, much like the response to asking if a square shouldn't be called an equi-angle rhombus rather than a rectangle with equal length sides. If the collision had been merely inferred (like that between Thetis and the pre-moon Earth) rather than observed using light (which moves at the presumed-fixed speed of light) then that would be different.

Oddly, I am now reading some of Larry Niven's Known Space series, in which some societies are dealing with the Galactic Core Explosion which will sterilize the galaxy some 30,000 years hence, and which was only discovered by use of a much-faster-than-their-usual-faster-than-light-drives drive on a trip to the Core for publicity and in hopes of investment capital. In this case, shotgun would be completely wrong.

Re:What happens if it turns out that dark matter i

[dwye]

So God is universal, omnipresent, and doesn't interact directly with people at all.

Sounds like the Unitarian-Universalists were right !

Only some of them. Others are not sure of versions of godhood that are entirely different.

Actually, I would call it The Force and say that George Lucas was right (since we can influence dark matter, by our own mass - maybe someone with midichlorians could have more influence?).

Dark Matter weak interaction leads to uncertainty

[DontLickJesus]

Don't know the double slit test? (Yeah right, geek) Go here : http://www.youtube.com/watch?v=DfPeprQ7oGc

In it, a photon targeting photo film through a double slit creates an interference pattern when left unobserved during the process. However, if one attempts to observe/detect the photon traveling through both slits, it only travels through one, leaving 2 standard lines. The typical take from this is that quantum uncertainty breaks down because the process was observed, forcing a choice to be made. However, there's no reason that photons must be the only particle exhibits this uncertain state, and I believe we're getting a glimpse of that here.

The reason quantum uncertainty cannot be observed at laboratory scales is because the time scales would allow us to violate causality, and the universe doesn't allow for that. If "dark matter" is a form of Boson-like material, which it definitely seems to act like, it would make sense that it could gravitationally interfere with itself in multiple galaxy collisions. The key being that nothing had the opportunity to stop or alter these interactions, but each interaction had multiple spacial outcomes with equivalent probabilities. "Observation" actually just denotes a probability of interference, and the different ultra-massive pulls from various galaxies would create the uncertain path (double slit), as all mass centers involved would have multiple possible paths ahead of them. Since we had no ability to stop it when it happened, we get the pleasure of watching it now.

Gravity, as I see it, is the inversion and/or scattering of particle uncertainty when highly interacting particles clump together. Physicists would say that any object still maintains the possibility that it could fly part at the electron shell level (theoretically) at any moment. Think if it as a massive object's footprint spreading forward into time. Less massive objects (like you and I) near the surface of the larger simply become statistics in the largest worst-scenario desegregation, and the probabilities of where we end up are much less complex than the massive core of a planet.

The smaller, brighter masses of the continuing galactic parts of collision mentioned in the article were likely sling-shotted through because of the massive gravitational pull of the early dark matter interference, which likely significantly subsided in strength as the dark matter uncertainty was reigned in by the pull of the gravity of the normal matter. Why? Since normal matter can interact with so many more particles/forces, It's level of uncertainty is reduced by the number of nearby particles which could interfere with it. Therefore, it's gravitational footprint would remain relatively static and condensed. This would cause the dark matter (by this time lumped as observed above) to be pulled like a jetstream as the densely certain mass imposed just a bit more certainty on the dark matter around it, reducing the net gravitational pull.

TL;DR; I propose that Dark Matter's low rate of interaction gives rise to gravitational interference. As an echo of quantum uncertainty, it gives rise to large fluctuations in gravitational fields acting on normal matter. Normal matter counteracts this gravitational interference through via higher levels of certainty imposing on dark matter. Uncertainty seems to be a property of particles most purely interacting with forces.

Re:Cosmic equivalent of the double slit test.

[DontLickJesus]

Yeah I suck, this is me.

Re:Observed Dark Matter?

[dudpixel]

We can't directly observe air aether...

FTFY

not even sure if it makes sense, but thought I'd have fun with the words anyway...

Re:Observed Dark Matter?

[Tablizer]

That's Dark Matter, not air.

Re:Not to be pedantic, but

[timq]

Similarly, in the vernacular:

mieren neuken (dutch) - to fuck ants
Korinthen kacken (german) - to shit raisins

Re:Observed Dark Matter?

[Muad'Dave]

No, but chilling air to liquid hydrogen temperatures is observing it.

Re:Observed Dark Matter?

[Muad'Dave]

I believe another salient quote from that same video document is "She's-a round, she's-a firm, she's-a fully packed!"