Researchers build computer simulation that shows a way to detect the birth of the first stars

Jun 21, 2012 by Bob Yirka report
The effect of relative velocity on the distribution of star-forming haloes. Image (c)Nature (2012) doi:10.1038/nature11177

(Phys.org) -- In the model astrophysicists and astronomers use to describe the history of the universe, the Big Bang is used as the ultimate starting point, which is believed to have occurred some 13.7 billion years ago. After that, things grow a little murkier as at some point atoms were formed, then stars, and then entire galaxies. The timeline for these formations has been difficult to gauge though as there is so little evidence for researchers to look at; still most agree that the first stars likely appeared somewhere in the neighborhood of a hundred million years after the Big Bang. Now a team of researchers has found that in creating a simulation on a computer, as they describe in their paper published in the journal Nature, they might have found a way to detect the signature of the very first stars to have formed.

In creating the simulation the team looked at theories that suggest that during the early stages of the development of the universe, and regular (baryonic) matter began moving at different speeds due to light interacting with them. Dark matter is believed to be mostly impervious to the impact of light, whereas baryonic matter gets pushed when struck. But because this change in speed was occurring during the time when stars were forming (due to clouds of gas bunching together from their collective gravity and pressure from dark matter) the number of being formed would be lessened, leading to a "lumpier" universe than has been previously thought.

The researchers used the relative differences in the speed of moving dark matter and baryonic matter and the way they believe radiation emitted from the earliest stars would have impacted those that came after, to calculate that the first stars would likely have appeared some 180 million years after the . Using that information they were able to show via their simulation that the radiation emitted from the first stars should be detectable in the 50 to 100 range here today on Earth. Unfortunately, there are no radio telescopes currently operating in this range, so the team has suggested that one such as the Murchison Wide-field Array in Australia be modified to detect such signals. Doing so, they say would allow researchers to actually listen for clues left behind by the lumpiness of early star distribution and gas interactions allowing them for the first time to detect the presence of those first stars to be born.

Explore further: Image: NGC 6872 in the constellation of Pavo

More information: The signature of the first stars in atomic hydrogen at redshift 20, Nature (2012) doi:10.1038/nature11177 . http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11177.html

Abstract
Dark and baryonic matter moved at different velocities in the early Universe, which strongly suppressed star formation in some regions1. This was estimated2 to imprint a large-scale fluctuation signal of about two millikelvin in the 21-centimetre spectral line of atomic hydrogen associated with stars at a redshift of 20, although this estimate ignored the critical contribution of gas heating due to X-rays3, 4 and major enhancements of the suppression. A large velocity difference reduces the abundance of haloes1, 5, 6 and requires the first stars to form in haloes of about a million solar masses7, 8, substantially greater than previously expected9, 10. Here we report a simulation of the distribution of the first stars at redshift 20 (cosmic age of around 180 million years), incorporating all these ingredients within a 400-megaparsec box. We find that the 21-centimetre hydrogen signature of these stars is an enhanced (ten millikelvin) fluctuation signal on the hundred-megaparsec scale, characterized2 by a flat power spectrum with prominent baryon acoustic oscillations. The required sensitivity to see this signal is achievable with an integration time of a thousand hours with an instrument like the Murchison Wide-field Array11 or the Low Frequency Array12 but designed to operate in the range of 50–100 megahertz.

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dogbert
1.6 / 5 (13) Jun 21, 2012
It is unlikely that the simulations will be useful since they are based on the existence of a substance which has not been detected or described despite continual efforts.

Despite this, if stars created after the big bang can be detected in the 50-100 megahertz range, such stars should be detectable with or without dark matter.
SpiffyKavu
5 / 5 (5) Jun 21, 2012
This paper tells us that we can expect the 21-cm line from this primordial gas to look different from what we expected (different spectrum) due to a different spread in velocities in the early universe. This shape of the spectrum will put constraints on the dark matter clumpiness (and therefore DM density/effective temperature/etc).
El_Nose
4 / 5 (6) Jun 21, 2012
We know how it acts on matter and on light -- we have seen it experimentally with gravitationally haloed light -- which started as a simulation. There is every reason to believe the simulations are right. We have never seen dark matter but we have been able to measure it's effects for years
dogbert
2.5 / 5 (13) Jun 21, 2012
No. We label gravitational anomalies dark matter. That does not mean we are measuring dark matter.

Dark matter its a kludge. The problem with a kludge is that people forget that it is a kludge and begin to believe it its real.
El_Nose
5 / 5 (3) Jun 21, 2012
Dark matter is a heck of a kludge my friend -- without it big bang theory goes boom, it can't happen, be careful before kevin catches wind of your beliefs.
A2G
2.2 / 5 (6) Jun 21, 2012
Dogbert. You have got it exactly right. Seeing anomalies means that something is not correctly understood. When you truly have the correct understanding of a system then you do not find anomalies. You predict them and so they are no longer anomalies.

I predict that DM will be proven to be one of the biggest scientific blunders of all time.
DTC
5 / 5 (2) Jun 21, 2012
Insert Terriva comment about aether theory here.
dogbert
2.5 / 5 (6) Jun 21, 2012
El Nose,
Dark matter is a heck of a kludge my friend -- without it big bang theory goes boom, it can't happen...


The big bang theory was developed long before we created dark matter.
Graeme
not rated yet Jun 22, 2012
Trying to receive at that red shift will be affected by a seriously reduced depth of field, 20 times less, however the linear sizes of things that far back should be expanded 20 times each way cancelling out the density of matter effect, which should be 8000 times denser then. The universe would have had a much warmer CMB at that time too. Another place to build a telescope for this could be in Antarctica, just keep away from the auroral zone.
kevinrtrs
1.4 / 5 (8) Jun 22, 2012
Since this paper assumes the existence of dark matter, does that mean that if the modification of the array actually delivers the expected signals, that such an assumption of dark matter will be vindicated?
If the array doesn't deliver, will it mean the opposite?
kevinrtrs
1.8 / 5 (14) Jun 22, 2012
El Nose,
You're absolutely right - dark matter is one heck of a kludge to fix up the shortcomings in the big bang model. For one thing - the bb cannot deliver stars, let alone galaxies, without invoking the magical dark matter and dark energy. Which means it basically cannot account for just about everything in the universe.

Saying things like "We've seen it's effects for years" doesn't help since you don't know what it is that is causing the effects. So how can you be sure it's not some miscalculation or misunderstanding of some other actual, real physical phenomena that was excluded in formulating the bb model?
El_Nose
4 / 5 (5) Jun 22, 2012
you down voted Kevin but he is right

-- Big bang theory was developed before dark matter was a theory

this is very true, doesn't mean that what i said wasn't true. Without DM the BBT doesn't work well based on current observations. The universe is too clumpy without DM in BBT. If you take out DM then we should be a lot more homogeneous. the anisotropies in the CMB, galaxy cluster velocity dispersions, large-scale structure distributions, gravitational lensing studies, and X-ray measurements of galaxy clusters -- all these issues that BBT has goes away with DM.

It was because of these issues that BBT almost went away. I repeat big bang simulations depend on DM being real.

-- Just because BB is the best theory we have, everyone knows it's incomplete. Stop approaching this like a high schooler and do some research before you retort. Find holes in statements and provide links to references...

or just vote me down because you don't understand physics.
El_Nose
5 / 5 (3) Jun 22, 2012
@ kev

Dark energy isn't magical it is more than a theory than DM by far - it is measurable - its a force with no creator

the mystery of Dark Energy is that we have no idea how to account for it or where exactly it comes from. -- and even that is a bad explanation... its measurable, directly measurable by the way.

DE is the energy of space. Space itself - if you took a ideal complete vacuum that had no matter in it no heat nothing at all -- it would still have energy -- this is DE.

Einstein predicted it and then altered his equations because he thought he must have gotten it wrong. He later called those alterations his biggest blunder. empty Space has energy,

-- look up the casmir effect --

Newton thought space was like a stage and was static -- Einstein said space interacted with matter and was proven in 2006 or '08 when NASA finally showed the earth did create frame dragging after 60 years of research. And now we know he was right about it having inherent energy.

Maat
3.3 / 5 (7) Jun 22, 2012
It is unlikely that the simulations will be useful since they are based on the existence of a substance which has not been detected or described despite continual efforts


I don't think you understand how simulations work or why we create them...
dogbert
1 / 5 (5) Jun 22, 2012
I know that a simulation based on inaccurate assumptions cannot be expected to provide an accurate model.
frajo
5 / 5 (1) Jun 22, 2012
It is unlikely that the simulations will be useful since they are based on the existence of a substance which has not been detected or described despite continual efforts


I don't think you understand how simulations work or why we create them...

Simulations are mathematical tools. Using them leads to mathematical results. Mathematical truths are not necessarily physical truths.
Maat
3.3 / 5 (7) Jun 22, 2012
I know that a simulation based on inaccurate assumptions cannot be expected to provide an accurate model.


Unless they are being used to test the plausibility of the assumption...

Gee, what a novel concept... Again, you don't know how simulations work or what we use them for.
Maat
3 / 5 (6) Jun 22, 2012
It is unlikely that the simulations will be useful since they are based on the existence of a substance which has not been detected or described despite continual efforts


I don't think you understand how simulations work or why we create them...

Simulations are mathematical tools. Using them leads to mathematical results. Mathematical truths are not necessarily physical truths.


Of course not, and if you think this is what I was implying you are far off the mark. You can make a simulation using known good values and one unknown variable and compare the result to reality to determine the feasibility of that unknown variable... this is one way in which we learn from simulations. They don't have to produce accurate results to be useful, producing inaccurate results is just as informative if the simulation is set up properly.
HannesAlfven
1.6 / 5 (7) Jun 23, 2012
It's very refreshing to observe physorg commenters who are skeptical of the dark matter inference. Many online commenters today confuse critical thinking for "crackpottery." Critical thinking is a process which includes questioning assumptions and listening to critics. When advocates of mainstream theories call somebody a crackpot for simply questioning an assumption in science, bystanders may learn from the exchange that they will be ostracized for thinking critically about mainstream theory. If the crowd refuses to stand up for peoples' rights to question assumptions in science, as well as the need to discuss alternative inferences in the face of underperforming theories, we all lose in the long run. The socialization of science can dramatically influence the questions we ask in science, and replace philosophy of science as a guide to reasoning with psychology and sociology. We can easily become our own worst enemies in science if we permit it to happen.

Thank god some get it.
Maat
2.9 / 5 (8) Jun 23, 2012
If a career physicist questions an assumption I will consider his objection credible... if some random person does the same in the comments section of a 3 paragraph news blurb I will consider it with far less credibility.

I am addressing this to everyone: If you want to be taken seriously here then it is YOUR job to convince me that your opinion is worthwhile. You can do this by providing credentials, or by establishing a history of intelligent comments. Several people here have done this... when AntiAlias speaks I listen, because he is consistently correct and has demonstrated his knowledge on many occasions.
frajo
3.7 / 5 (3) Jun 23, 2012
If a career physicist questions an assumption I will consider his objection credible... if some random person does the same in the comments section of a 3 paragraph news blurb I will consider it with far less credibility.
This "high priest approach" to knowledge cannot provide the same degree of certainty as the method of falsifiability. The Vulcan hypothesis (a lot of "career" scientists involved) may serve as an historical example.

Mathematical feasibility by simulation doesn't replace falsified physical hypotheses.
Otherwise scholastic dialectical considerations of the number of angels on a needle's tip need to be taken serious again.
Maat
3 / 5 (6) Jun 23, 2012
frajo... It's a simple fact that some people's opinions are worth more than others on specific topics... don't take what I said and turn it into a simple appeal to authority. I never said to completely ignore everyone who isn't a career physicist, I said I will (rightfully) weigh their opinion ahead of that of an average Joe.

The fact is, most people here are not equipped to falsify most theories in physics and cosmology... which at least requires that you understand the theory. I don't think that even 2% of the people who post here actually UNDERSTAND the big bang theory beyond a common media-derived understanding (including the history of discoveries and the evidences in favor of it), so when the majority of physicists and astronomers agree with the big bang theory and a handful of people with questionable credibility object to it on grounds that don't make sense if you actually understand the theory I will rightfully take it with a grain of salt.
HannesAlfven
2.1 / 5 (7) Jun 23, 2012
Re: "If a career physicist questions an assumption I will consider his objection credible... if some random person does the same in the comments section of a 3 paragraph news blurb I will consider it with far less credibility."

The problem with your approach here is that it fails to address the mistakes that are embedded into our textbooks, which are advocated by established, credentialed theorists. You've reduced critical thinking to taking a poll of scientists. When theory dead-ends, credentials are no longer useful.

Furthermore, credentials can be used to back up just about any claim. That's because even Nobel laureates disagree. In fact, science badly needs disagreement. The worst-case scenario is widespread agreement on a controversial, uncertain topic, for agreement tends to dampen the process of asking questions.

There is unfortunately no shortcut to thinking. The textbooks have mistakes. Science is not a process of placing faith in somebody else's thoughts.
HannesAlfven
1.7 / 5 (6) Jun 23, 2012
Re: The fact is, most people here are not equipped to falsify most theories in physics and cosmology... which at least requires that you understand the theory. I don't think that even 2% of the people who post here actually UNDERSTAND the big bang theory beyond a common media-derived understanding (including the history of discoveries and the evidences in favor of it), so when the majority of physicists and astronomers agree with the big bang theory and a handful of people with questionable credibility object to it on grounds that don't make sense if you actually understand the theory I will rightfully take it with a grain of salt."

@Maat, the problem pertains to the way we are teaching physics today. Students are memorizing the processes of problem-solving, instead of learning the interrelationships between concepts. In a study of 1000 undergrad physics students, a concept-based exam demonstrated only a marginal 14% improvement from taking a semester-long physics course.
HannesAlfven
1.7 / 5 (6) Jun 23, 2012
If you don't understand the concepts of physics, then you lack a foundation upon which critical thinking can occur. A person cannot question assumptions when they don't understand the fabric of the concepts themselves. Physics news sites (including physorg) and physics textbooks are actually part of the problem, insofar as they consistently fail to distinguish between claims, inferences, speculations, experimentation and assumptions. If all they did was place some sort of tag above each of these within their articles, we'd finally start to see some improvement. But, these aggregating news sites exist to service that which our educational institutions have already created. And since the textbooks are making the exact same mistake, we're going to have to wait for somebody else to fix the problem. The thing is: I don't know that there is actually any desire amongst the mainstream physicists to have people better understand the Big Bang, because then they can criticize it.
HannesAlfven
1.5 / 5 (6) Jun 23, 2012
I also need to mention that college-educated specialists tend to have naive views of how science works in the real world. Peer reviewers have far less power than the specialists like to imagine, because they don't control the money. The guys with the money get to pick and choose the direction that the science goes in, as well as the peer reviewers, and they oftentimes ignore the advice of the peer reviewers.

Furthermore, politics is a big problem for all large institutions of people. Science happens to be one of those, and the scientific method does not save us from it. Jeff Schmidt, a former editor of Physics Today for 19 years (one of their best at the time), wrote a book detailing the politics of our physics graduate program, called "Disciplined Minds." While most laypeople completely ignored it, professional scientists did not. In fact, around 1000 researchers wrote letters in support of Jeff (including Noam Chomsky) when he was sued by the American Institute of Physics.
HannesAlfven
2.1 / 5 (7) Jun 23, 2012
Jeff Schmidt in an interview, from http://www.julesn...6489.htm

"It seemed like the best of my fellow graduate students were either dropping out or being kicked out. And by best, those were the most concerned about other people and seemed less self-centered, less narrowly-focused, most friendly people...they seemed to be handicapped in the competition. They seemed to be at a disadvantage not only because their attention was divided, but because their concerns about big picture issues like justice and the social role of the profession and so on, caused them to stop and think and question, whereas their unquestioning gung-ho classmates just plowed right through with nothing to hold them back. As I mentioned, theres about a 50% drop-out rate for students entering University programs in all fields; and what I found was that this weeding out is not politically neutral. To put it bluntly, the programs favor ass-kissers"
HannesAlfven
1 / 5 (4) Jun 23, 2012
To place some extraordinary confidence in the opinion of somebody with a credential is to imagine that, if and when it is their turn to step off the stage, that every single one of those establishment scientists will admit that they are not the expert in the event that foundational flaws are discovered within our cosmological theories. The closer to the base of these speculative theories that a problem occurs, the less likely -- in practice -- that establishment physicists are to even acknowledge, or have a discussion of some potential problem. That's because so many decisions have already been made about what to focus on by this establishment, that to admit some of these errors represents an admission that the experts are no longer the experts.

That decision to take on a narrow focus was made to make the entire organism of science more efficient. The push towards consensus in science seems to have started with the fallout from the aether debates.
HannesAlfven
1 / 5 (4) Jun 23, 2012
But, education reformers have noticed an unsettling side-effect of this decision to get everybody onto the same bandwagon: Our students understand the "what", but they appear to not understand the "why". When you teach kids one worldview, they memorize it. But, teach them two, and they can be asked to compare and contrast them. This process of comparing and contrasting worldviews in science is a skill which we are obligated to train our students in if we want them to be able to critically think in terms of scientific paradigms, and find the errors in the textbooks.

This is how we teach critical thinking in literature classes: By helping the students to understand the worldviews of other people. The decision to limit students' exposures to competing theories in science has had unfortunate consequences. And until we figure out how to teach students how to compare and contrast two different worldviews in science, we will fail to fix the remaining problems in our scientific theories.
HannesAlfven
1 / 5 (4) Jun 23, 2012
Compare a scientific paradigm to a box. In order to appreciate the box's features, we need to compare it to other boxes. If we are stuck inside of the box, and never even attempt to leave it, then we have no idea how the box even looks from the outside. We cannot intelligently criticize it.

Now, let's imagine that it took us a couple of years to learn about the contents of the box itself. We're invested in these ideas. Psychology studies (learned it from physorg, actually ...) demonstrate that people will tend to favor the box over competitors, even when they don't know what the competitors are. Another physorg psychology press release explains that once people make a decision, they adjust their views to support it. The decision to read about something is sufficient, by itself, to induce somebody to agree with it.

This is why we desperately need to get away from thinking inside of the box. Everybody is susceptible to these problems. Nobody is immune.
HannesAlfven
1 / 5 (4) Jun 23, 2012
The truth is that all sciences are not equal. Tell me with a straight face that we should treat the subject of dark matter like the subject of automobile engines. The difference is that some concepts are more elusive to our senses than others.

Where concepts cannot be easily sensed, our minds will apply our pre-existing cultural, psychological and social context to that item. This is called hermeneutics, and this is how bias creeps into science.

What this means is that for disciplines of science which deal with elusive concepts, we are obligated to acknowledge this inherent uncertainty. And the best place to do this is at the inferential step. In other words, in uncertain disciplines like cosmology, we are obligated to consider competing paradigms.

But, to be clear, I am NOT advocating that we stop filtering information. What I'm advocating is that we step out of these strict information bubbles which we've created for ourselves, when we talk about uncertain subjects.
HannesAlfven
1 / 5 (4) Jun 23, 2012
The problem becomes very serious for mainstream science when you look at its structure. We badly depend upon what's happening at the two extremes in scale, in order to explain the big picture. And yet, we can't even see anything that is happening from around 10^-19 meters down to 10^-35. There is a similar problem at the other end, for parallax stops working at just 1% the diameter of the Milky Way (!). The positions of everything beyond that is, strictly speaking, *inferred*, based upon the framework.

So, not only is there great uncertainty at the two extremes, but we then depend upon knowing what's happening there in order to formulate our scientific framework. And this is where it gets very ugly: All practicing scientists assume this scientific framework. Those who refuse to are weeded out in the PhD program (see Disciplined Minds).

The problems of cosmology (and the other big questions in science) are far too complex to just take a survey of the opinions of the experts.
HannesAlfven
1 / 5 (5) Jun 23, 2012
I write extensively on physorg about the Electric Universe. This is very unpopular. I'm keenly aware of it every day that I do it. How could I not be?

People like to imagine that I am a crackpot. But, what I am doing is exposing people to a different worldview. I'm providing a service. People can simply choose to disagree with what I'm saying, but the day that we stop trying to contribute to one another's knowledge is a very sad day. The mainstream doesn't realize it, but it badly needs people like myself (who talk directly to theorists) to act as thoughtful intermediaries. The theorists need to spend their time working and thinking.

Theories don't just arrive from the stork, ready to be judged as perfect and obvious by the public. There is always one or more reasons why the public doesn't understand the theory. Oftentimes, the theory is malformed to begin with. But, every once in a while, there are good ideas which are being thrown out with the bathwater.
HannesAlfven
1 / 5 (6) Jun 23, 2012
When you are on this side of the fence, you start to notice things which you don't while on that side (the conventional side). You start to notice many things about human psychology and sociology, which you never spend even a moment thinking about when all you do is advocate whatever it is that is conventional.

If you don't believe me, then just do it: Identify an interesting inference which you know for a fact remains unresolved. Go onto the forums and advocate some completely worthwhile against-the-mainstream position. Then, carefully watch the nature and content of the responses. They won't look anything like you expect them to. You are not observing logic or reason.

What you will almost surely notice is that people use shortcuts to contemplate complex problems. Each person's subconscious is trying to guess the results of their own actions, at all times. This keeps us alive, but it also screws up our ability to think about extremely complicated questions.
Anda
not rated yet Jun 23, 2012
People who have their truth established in one sense or another make me laugh.
We just don't know exactly and we keep on learning every day.
And the way to do it is formulating theories, realizing experiments and simulations.
Mastoras
5 / 5 (2) Jun 24, 2012
I know that a simulation based on inaccurate assumptions cannot be expected to provide an accurate model.

Um, you dont seem to realize it, but you show yourself unfamiliar with what is an assumption.

It is highly misleading to think that an assumption can be said to be inaccurate, because that presupposes a way to conclude it is inaccurate. But the only way to conclude that is to test it. ALL assumptions are to be tested. It is after this that we may say this one is rejected, this one is inaccurate, etc.

We are not testing only accurate assumptions, because we have no way to know which are these.

For God's sake!! I have all the good will to explain to people that which I know. But I'm seek and tired seen the same points raised again and again, always based on a misunderstanding of what science is. Please, do some homework. Actually, these days I'm doing exactly that.
-.
dogbert
1 / 5 (5) Jun 24, 2012
Mastoras,

The least effective retort is the "you don't understand" retort.

Of course I understand testing hypotheses. I also understand what science is.

I also understand that dark matter is a kludge created because our observations of stellar movement do not fit our models of gravity. Rather than trying to discover why our models fail, we instead created an imaginary substance to correct our models. The kludge nature of dark matter is evident by our current inability to predict. Instead we must observe and then create the amount and distribution of dark matter to normalize our observations.

My comment was only on the order of "If you base your model on faulty beliefs, you cannot expect accurate results".

Science seeks to understand reality, it does not seek to validate bias.
Mastoras
5 / 5 (2) Jun 24, 2012
dogbert,

I also understand that dark matter is a kludge created because our observations of stellar movement do not fit our models of gravity.


People who call an hypothesis a kludge (should I look that in a dictionary before I post?) do not seem to understand what an hypothesis is.

If they were, they will have said "This hypothesis of dark matter has these and these problems. For these reasons, I propose this other hypothesis."

The above will have been a perfectly acceptable part of a logical discussion. Instead, they say "Ah, but you will have mistaken results because you base your analysis on a hypothesis".

But, of course I am basing my analysis on a hypothesis. That's exactly why the hypothesis was introduced in the first place: to allow us to explain things. And it was meant to be used.

Attacking science because it uses hypothesis, only shows a less than appropriate understanding of what a hypothesis is and what science reasoning is.
-.
dogbert
1 / 5 (5) Jun 24, 2012
No, Mastoras, dark matter is a kludge -- not a hypothesis.

A hypothesis can be tested by its ability to predict.
A kludge is identified by its inability to predict.

The dark matter kludge cannot predict movements of stars nor the bending of light. Only after the observations are made can the amount of imaginary dark matter be calculated.

Hypotheses are good.
Imaginary mass and all other kludges are bad.
stellar-demolitionist
5 / 5 (1) Jun 25, 2012
Dogbert,

The interpretation of yet unmade results could determine the properties (or even existance?) of dark matter. This is clearly stated in the article and the first few responses.

Scientifically "kludge" has no relation to "hypothesis", the term is simply not used. I'm not sure what we might call dark matter scientifically. Perhaps "placeholder" is a more apt term.

The "dark matter effect" was first seen in galaxy rotation curves and two viable explanations remain: long-distance modifications to gravity (MOND, MOG) and (one or more types of) matter that does not interact with photons. There is growing evidence that some sort of "non-glowing" matter exists: gravitational lensing maps of galaxy clusters, the Bullet cluster, large scale structure, etc. In the mean time the theorists will continue to identify DM candidates, the experimentalists will build experiments, the modelers will compute and the observers will look for consequences of DM.

This is one of those tests of DM.
Pyle
5 / 5 (3) Jun 25, 2012
The "dark matter effect" was first seen in galaxy rotation curves and two viable explanations remain: long-distance modifications to gravity (MOND, MOG) and (one or more types of) matter that does not interact with photons.

Only two? I'm sorry. In this instance we don't know what we don't know. Great post though s-d.

The term Dark Matter, kludgey though it may be, encompasses a whole host of hypotheses including things like WIMPS, MACHOS, etc. Modified gravity might label another side and could include MOND, TeVeS, STVG, MOG (my favorite), etc. Yet other categories could be the scoffed at aether theories and the Electric Universe.

To date, DM theories seem most compatible with our observations. The gravity theories receive some attention and have been largely excluded by observation. Aether, *giggle*. Regarding EU, advancements in plasma physics are constantly incorporated into our cosmological models, but most EU proponents are nutters, going too far.