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Dark Matter Stars in the Early Universe?
OriginalArlen writes "UniverseToday reports new research which suggests dark matter could have condensed to form 'dark stars' in the early universe. These stars would have been very massive and burned very slowly, fueled by non-fusion reactions, they could still be with us. Astronomers hope to better constrain theories of early galaxy and star formation with observations of gravitational lensing events caused by these ghosts of the primordial universe."
Of course, that's where all of our packing material comes from.
Thank God for evolution.
"Nothing for you to see here. Please move along."
Indeed.
Hmm... what if we discover a star like the one Asimov described in Nemesis? Yes, I know it wasn't a dark matter star, but they didn't see it, either.
So I guess John Carpenter created the universe? http://imdb.com/title/tt0069945/
The Grateful Dead predicted the existence of Dark Stars about 30 years ago.
TFA brings up a good point, all this dark matter had to have condensed into big star-like masses and should still be around but it wouldn't just be pure dark matter there would be hydrogen and helium too and on the other hand stars like our sun should have dark matter in them too so where is it? if this dark matter is indeed doiung what they say why the heck heven't we detected it in some way?
Sigs are too short to say anything truly profound so read the above post instead.
The whole article sounds like a solution in search of a problem. It talks about "Dark Matter" as though the mysterious substance's properties were well-defined, even going as far as positing stars fuelled by "dark matter annihilation, instead of nuclear fusion". And then TFA says "If these dark stars are stable enough, its possible that they could still exist today".
I propose that dark matter is actually composed of jellybeans and M&M's, and that the first massive objects were stars fuelled by the crushing force of the crunchy shells of the M&Ms piercing the relatively soft outer coating of the jellybeans. Gravitational separation eventually turned the masses into giant Cadbury Creme Eggs.
Other than being completely silly, am I making any fewer wild guesses than the Dark Matter Annihilation folks?
Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
http://en.wikipedia.org/wiki/Weakly_interacting_ma ssive_particle
The bastard children of Dark Helmet and Lone Star?
Best Slashdot Co
Damn! You can't find a good Lovecraft Quote when you really need one! ... off to the library!
TFA brings up a good point, all this dark matter had to have condensed into big star-like masses and should still be around but it wouldn't just be pure dark matter there would be hydrogen and helium too and on the other hand stars like our sun should have dark matter in them too so where is it?
wizardforce's Mom: "wizardforce, I have told you a thousand times: take big breaths and speak slowly."
Darkstars predominated the early universe. A new tenet for the Church of the Subgenius!
Dark Star crashes...pouring it's light into ashes...reason tatters...the forces tear loose from the axis...
If your car is powered by the annihilation of elementary particles and anti-particles, kudos to you. For myself, I'm not sure to what extent these objects deserve to be called ``stars''.
Just wondering but if they are are massive and burn slowly wouldn't they tend to collapse into black holes? If they don't put out enough heat to counter their gravitational field they should collapse. If so they may be the cores of the super massive black holes at the center of many galaxies. Just and idea since there where no numbers given in the article.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
On \. OriginalArlen reports the news. I look at the linked website, called Universe Today and I see that there is one "publisher" by the name of Fraser Cain. Following the link there, finally, I get to the article on the arxiv, the definitive source of new physics papers. So to get to the source, it takes three jumps. So what has Fraser Cain done for us? Watered down the content? Couldn't OriginalArlen read the article and write a gist himself/herself? Or is Fraser Cain the same person as OriginalArlen? Reading the original article, I find "some" correlation on what ends up on \. and what is in the article. Or is this not the point? If I had to write a review for this article, I would have said that the last sentence of the abstract is what is most important: "A ..star .. detectable via annihilation products (gamma-rays, neutrinos, anti-matter) possibly in combination with hydrogen lines."
The brilliant thing about this article is that these theorists are cooking up something that is actually detectable! Something that can be tested and hopefully will! *Finally* congrats to Douglas Spolyar, Katherine Freese and Paolo Gondolo, who *wrote* the article. (No, I dont know any of them. But isn't it time we cited those whose ideas we regurgitate?)
Here is the PDF: Dark matter and the first stars: a new phase of stellar evolution
Here is the abstract:
I'm just an armchair physicist, but the article talks about dark matter annihilation.
What exactly is/was the dark matter annihilating with?
I thought antimatter and matter could annihilate...
Would the dark matter in fact be the regular matter that antimatter annihilates with in the proposed scenario?
I don't know the meaning of the word 'don't' - J
Ok, so say you are not a physicist, you can still read the article. It may have equations, but it is still English: http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.0521 v1.pdf
The authors say: "The nature of the cold dark matter in the universe is as yet unknown. Weakly Interacting Massive Particles (WIMPs) are possibly the strongest candidates, as WIMPs that were in thermodynamic equilibrium in the early universe automatically provide the appropriate relic abundance to give the observed matter density. More- over, WIMPs have a natural origin in particle physics, e.g. neutralinos in supersymmetric models are excellent DM candidates. [..]T he details of the interactions and masses of the neutralinos depend on a large number of model parameters. In the minimal supergravity model, experimental and observational bounds restrict the neutralino mass m to 50 GeV-2 TeV, while the annihilation cross section v lies within an order of magnitude of h vi = 3 × 10^-26cm3/sec (except at the low end of the mass range where it could be several orders of magnitude smaller). "
So the authors make it clear that they are working under a set of assumptions, which are now fairly well accepted in the astrophysics community. Yes, maybe, these set of assumptions are wrong and if they are, their nice constructed dark stars would not exist.... If the annihilation cross section was very very high, then all dark matter would have self-annihilated by now. So there are bounds on that. Yes, it is theoretically possible still, I suppose, that dark matter may not self-annihilate! That makes it harder to detect! Most favored particle physics phenomenology would suggest that there should be some annihilation cross-section, on the order of magnitude suggested by the measured strength of the weak-forces. It turns out that this annihilation cross section is low enough that most dark matter would have survived to this day after the ~14billion history of the universe.
A sufficiently advanced civilization that doesn't destroy itself first will inevitably optimize their environment to the point of harvesting every last drop of energy from their star(s), such that we can't detect anything but the gravitational effects.
This mysterious "dark matter" structure is termed a Matrioshka Brain (aka: Dyson Sphere).
I understand that this theory's still a bit too shocking for many to seriously consider, so "exotic particles" - or ANY other explaination - it must surely be.
Power to the Peaceful
Does it seem weird to anyone else? Now I haven't stayed up to date with dark matter, but they keep insisting that it MUST be there. It almost seems to be the ether that was claimed to be around us before Einstein blew that one open.
Dark matter, dark stars.... next there will be dark light!
Engineering is the art of compromise.
someone beat ya to it by like an hour...
We're matter.
But it doesn't matter.
With apologies to Captain Beefheart.
Dark Matter is something that physicists have used, to explain things that don't add up in calculations about the movement of galaxies and the expanding of the universe.
I have an alternate explanation that explains the concept that the universe is expanding at an ever-increasing rate, Gamma-ray bursts, and the background noise in the Universe.
Namely: There wasn't ONE big bang and there isn't just ONE universe. I'm not talking about extra dimensions -- but that the universe that we experience is just one Cluster, or "bubble." Our Big Bang was a regional event, and we can't see beyond the Time/Space distortion of it's shock wave. At some point, billions of years in the future, we may encounter the diluted shockwave of another Big Bang (we'll register it as a large-scale Stretching and contracting of space, as though everything were all of the sudden in a larger gravity well and then in less of one) and then see stars from another "Universe" and their Red-shift will show them coming toward us.
Galaxies are pushed outward more than they should, because larger objects are affected at a greater distance -- while small objects are much more effected by the closer objects. So any gravity detection, say, on earth or of an earth-sized object, would not detect the massive but distant effect of another Universe pulling on galaxies of our own. Thus, Galaxies are moving outward at a faster rate than is explainable from Big Bang theory.
The concept of this being an Open, or Closed universe is moot -- we are in a sea of "bubbles." And our Universe -- or Megaverse, is much more massive than anyone can imagine.
>> However, there may be Neutron clusters of unattached matter. Or "closed-loop" pocket galaxies. And these would be "Neutral" to our Universe.
>>"ad space available -- low rates!!!"
If there was non-fusion going on, would it emit light with a characteristic white-body spectrum?
How could dark matter form a star made of hydrogen or helium? I was under the impression that dark matter wasn't actually "matter" per se but rather the name assigned to a phenomena that causes gravity where there is no mass. This reads to me more like an anti-matter star... but then again, I'm no scientist here. Just some guy reading slashdot.
I can't help but see parallels between dark matter and the (al)chemist's Phlogiston theory. Phlogiston was used to account for quantitative errors in chemical reactions. Funny thing was, every (al)chemist had his own measurements for its properties, until our understanding of chemistry improved. I wouldn't be surprised if the dark matter theory were eventually tossed out the window because our understanding of gravity improved.
The purpose of dark matter is to explain why spiral galaxies can rotate as a fixed plate. Until you can actually observe the particles or somehow conclude that they do indeed exist (and speculative NASA press releases with colorized images do not count), we should avoid further speculation about their role.
We cannot prove that dark matter exists with thought experiments. It requires the construction of equipment or laboratory work, or possibly even careful interpretation of observations. But, regardless of how many astrophysicists need PhD's, we should not encourage any further speculation about dark matter until it is demonstrated to exist -- for everything these new theories touch will themselves turn into speculation, and we will confuse ourselves more than we already have about the level of confidence we can place in our theories. What if we do decide to invest lots of astrophysicists into thought experiments about dark matter's role in the universe? Then, you will have effectively created a group that will lobby for the existence of dark matter even when the weight of the evidence is against it.
In other words, speculations should be based upon some sort of observation. Dropping hints about what a dark matter star might look like is just a clever way of trying to stake out terrain within the astrophysics community.
"A man cannot begin to learn that which he thinks he already knows." --Epictetus, 1st Century A.D.
The "missing mass" of the universe is energy stored and utilised by intelligence. This knowledge will not stop the funding drive in our tiny corner of the universe however.
Besides Dark Matter, isn't a change to the laws of gravity a bit more elegant solution to why galaxy's don't fly apart? Gravity doesn't obey Newton's laws on the very small scale (atomic), so why should they be expected to on the very large scale (galactic)?
Every time I see this stuff I'm always curious if there is a dark matter explanation of why Voyager is slowing down more than Newtonian gravity would predict. If not, is some physicist going to come up with some more imaginary unsee-able stuff to explain that away, too?
Plasma physics has better explanations and models for all this crap. www.thunderbolts.info www.holoscience.com - this one is by a nobel prize winner, so shut up.
Sure, Dark Matter is the star of the show, but we all know he would be nothing if it weren't for the supporting cast, and the great script.
Just because you can, does not mean you should.
"'dark stars'... 'they could still be with us'... 'ghosts'"
Geez, with Lucas announcing that more Star Wars movies are coming, it's sad that /. has been infiltrated by the Sith.
These are not the sequels you are looking for.
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See Clowe, Douglas et al (2006). "A Direct Empirical Proof of the Existence of Dark Matter," The Astrophysical Journal, ISSN 0004-637X, 648 (September 10): L109-L113.
It was big news at the time so Google will find you plenty of commentary online.
My own instincts suggest that we will eventually come to realise that dark matter and "dark energy" are as close as we will ever get to the main game in town and that baryonic matter will come to be seen as just the scum on the pond.
-- Our systemic servants do not good masters make.
You just blew my mind.
The moon--as in, Earth's moon--is just normal matter that doesn't glow. Oh, and Earth is too! Neither are dark matter.
That's not true. Earth does glow, quite strongly, in the infrared. The moon glows too, although at a slightly lower temperature (and thus longer wavelengths) due to lack of greenhouse effect.
However, Earth's infrared glowing is of course due to the sun's fusion output. Ie, Earth is in equilibrium, where it radiates as a blackbody the same amount of energy it that it absorbs from the sun.
So (as far as I know) a dark-matter planetoid at the same distance from the sun as Earth wouldn't have this infrared glow, because it wouldn't absorb solar photons. It would just exert a gravitational pull (or maybe have some other exotic effects). So you are correct, though, about dark matter being different from non-glowing (ie cold) 'regular' matter.
make world, not war
I'm probably talking out of my own dark star here, but can the additional gravity observed not be caused by parallel universes? That way, the dark matter exists (possibly as normal matter we just can't see) in parallel universes, and we observe the effects of its gravity on the visible matter in our universe.
I suffer from attention surplus disorder.
I wonder if somehow the dark matter isn't so much dark mass, but perhaps its purely electromagnetic in nature. We know photons have mass because they interact within gravitational influences. Do modern predictions about the universe take into any account all of this "mass" within transitory electromagnetic radiation? I would think it is measurable to some degree and therefore its influence predictable. And due to the doppler effect the gravitational effects of light should not necessarily be in a linear direction to their origin.
Could that mean excited antimatter might form some sort of an anti-photon, too? It would be intrigueing to think that an anti-photon pair comes from the nether to collapse upon its own origin the reverse that a photon pair spreads out from its origin and reaches out to infinity.
Gravity? Not quite. A bunch of tiny, non-interacting point masses would not coalesce at all. They would just buzz around each other forever, maintaining their original net kinetic energy, momentum, and angular momentum.
In order for dark matter to coalesce, it must do more than just "annihilate". There must be a mechanism for individual particles to lose kinetic energy. Ordinary matter does this through electromagnetic radiation and chemical bonding. The paper does not really explain how dark matter could do this.
However, a concentration of dark matter could, via annihilation, produce an outflux of radiation which prevents the normal collapse of ordinary matter for awhile. I think that's really the point of the authors. It's not accurate to call that a "star". It would not be localized, except to the extent that the dark matter happens to be concentrated in some areas. It would be more like a vast, glowing soup.
I'm confused, if we don't know what dark matter is, or if it even exists - why do we know that it would burn slowly?
Ace
Some sense at last. I just can't understand why rational people accept dark matter theories at face value, but claim to reject notions like 'ghosts' or 'god'.
Hell, here's my theory: Dark Matter = God. He's everywhere, invisible, and keeps the universe together! See, explains everything really.
The interesting thing about the whole dark matter episode, is that it probably gives an insight as to how religions form. Someone has a wild idea, that someone else expands on, that someone else tries to validate, that someone else uses as doctrine, that someone else teaches, that someone else uses to explain a wild idea...scary really. Eventually you end up with so many layers of analysis and reference that everyone's forgotten that the *original* idea was bunk. It's like an upside down house of cards.
lemonade was a popular drink and it still is
I can't help but wonder if there's an entire dark matter universe coexisting with ours, filled with dark matter stars, and dark matter planets, and maybe even a form of dark matter life and only tied to this universe through the gravitational force? Ever since I read that they'd confirmed the existence of the stuff, I've wondered if we'd find a twin universe hidden under ours.
Discovering for certain things like that might change the way I look at the universe.
It's been a long time.
Because there is evidence, lots of it, for its existence.
Hell, here's my theory: Dark Matter = God. He's everywhere, invisible, and keeps the universe together! See, explains everything really.
But, see, real astrophysicists are a bit more discerning. We've been able, through single galaxy dynamics, cluster dynamics, and gravitational lensing, to actually map out the distribution of this stuff. It's actually really interesting if you care to read the papers.
The interesting thing about the whole dark matter episode, is that it probably gives an insight as to how religions form. Someone has a wild idea, that someone else expands on, that someone else tries to validate, that someone else uses as doctrine, that someone else teaches, that someone else uses to explain a wild idea...scary really. Eventually you end up with so many layers of analysis and reference that everyone's forgotten that the *original* idea was bunk. It's like an upside down house of cards.
I'm glad that your idea of what science is really like is completely wrong. We're not all completely stupid. If we were, this field wouldn't be nearly as fascinating.
Although I'm not an astrophysicist, I have studied astrophysics as an undergraduate and know some things about dark matter theories and cosmology. You are absolutely correct in saying that dark matter must be non-baryonic under current models. Baryonic dark matter is excluded because big-bang nucleosynthesis models (which take observed primordial elemental abundances as input) show that only ~4% of the mass of the universe can be baryonic matter.
You are, however, incorrect in stating that dark matter shares no properties with ordinary matter besides gravity. All energy, including electromagnetic radiation and dark energy, affect the curvature of spacetime. Dark matter also has the property that it behaves in the same way as matter when the universe expands, i.e. that its density decreases as the cube of the scale factor (which determines the rate of expansion). Ordinary radiation and dark energy each behave differently in this regard, so dark matter is indeed uniquely matter-like in a very important way. Aside from galactic rotation curves, very good data from the WMAP project that studies the cosmic microwave background has determined that ~30% of the universe must be matter-like. Combined with the BBN studies, this means that 26% of the universe, by mass, is dark matter, which thus outnumbers ordinary matter by more than a factor of 6.
You are also incorrect in assuming that we haven't found dark matter. There is actually a very excellent photo of colliding galaxies that shows convincing evidence of dark matter. The caption does a decent job at giving an explanation of the photo's significance. If you want a more thorough explanation, both of the photo and why the result is significant, I recommend this blog maintained by several well-known cosmologists.
I would rather be killed by a terrorist than enslaved by my government.
Kardashev Scale
Dacelo
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So if one of these stars where big enough, we could have a Dark Black Hole?
Eep!
You raise a valid point about why we haven't seen any on earth. Well, they *are* all around us. They do not "cluster" as much as normal matter gravitationally so their concentration is not dense. We can not detect them directly through their gravitational influence, as gravity is too weak. Most experiments try to detect them through their weak interactions and hopefully soon will. There is an incredible amount of effort in this experimental effort right now.
... Until we have some of this stuff isolated in a laboratory, it only exists as a mathematic abstract.
... Let's quit all this deep-space navel-gazing and isolate some dark matter. Where's the oil-drop experiment of the new millenium?
I find it interesting that some people think that something isn't "real" unless it is seen in the lab.
Dark matter likely interacts only through the weak force and gravity, much like the neutrino.
Neutrinos cannot be "isolated" - but their existence can be detected indirectly through their (rare) interactions with other particles in detectors. That's perfectly valid, but why is it somehow more "real" than detecting a particle through its gravitational interactions?
Dark star crashes
pouring its light
into ashes
Reason tatters
the forces tear loose
from the axis
Searchlight casting
for faults in the
clouds of delusion
shall we go,
you and I
While we can?
Through
the transitive nightfall
of diamonds
Under present models, dark matter isn't matter at all!
Of course it is. You just have a restricted definition of "matter" which excludes, for instance, neutrinos. Neutrinos are massive fermions and deserve the label "matter" just as much as electrons do.
Under present models, dark matter exists only as a mathematical fudge.
It's not a mathematical fudge. There are a number of theories which naturally contain dark matter-like particles, completely apart from any motivation to explain the astrophysical observations. For instance, the Standard Model itself may well have to contain as-yet unobserved axions which are prime dark matter candidates, in order to resolve the strong CP problem. Also, there are a number of motivations coming from the Standard Model hierarchy problem and grand unification which suggest the existence of supersymmetry, which would provide other prime dark matter candidates. Neither of those motivations have anything to do with intentionally "fudging" the particle content of the theory to make astrophysics work out right.
Simply put, if there is so much dark matter in the universe, why can't we find some? Statistically speaking, there should be some right here on Earth!
Not if it's neutrino-like. Then it's hard to detect (extremely low interaction cross section) and doesn't tend to stick around in one place. Also, while most "regular" matter is confined to the galactic disk, dark matter is likely distributed throughout a spherical halo, meaning not too much of it happens to intersect the galactic disk (where we are). There are direct dark matter searches, but it's very far from a foregone conclusion that they will be able to detect dark matter. Simply put, just because it's abundant doesn't mean that it's easy to find.
It makes almost as much sense to say that there is a parallel material universe, slightly overlapping our own, that only interacts with our universe on a gravitational level.
Actually, that idea has been proposed, but there is much less motivation for it than there is for dark matter, as dark matter candidate particles exist quite naturally in the Standard Model and the most plausible extensions thereof. Also, the "parallel material universe" idea isn't really a substitute for dark matter (it was proposed for other reasons), since a "parallel universe" with "normal" matter in it doesn't behave like dark matter does!
They go on to explain why they think the bullet cluster means we've "found" dark matter, but frankly the problem remains.
So? Unless you can come up with a feasible alternative explanation (and to my knowledge, there isn't one... I don't believe any of the popular MOND theories can explain the Bullet Cluster, though I may be wrong), the Bullet Cluster provides strong evidence for the existence of DM, whether or not you find the theory aesthetically pleasing or not.
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http://www.kbi-net.co.jp/KBI_Site/page01/face.jpg He is the world's worst phimosis. His cock is more stinking than anyone in the world. He is a gay. He sucks penes of an employee. As for him, ejaculation in a vagina to a woman employee is daily work. Therefore he has a large number of illegitimate children. He receives a large amount of bribe from the prefectural governor and the mayor. His clans are dependent on incest. His favorite food is a live cockroach. His close friend is Kim Jong Il and Osama bin Ladin. They conspire to annihilate a Japanese. Please fire bunker-buster into his hiding place right now. His hiding place is here. Bin Ladin is here, too. http://local.google.co.jp/maps?f=q&hl=ja&q=%E4%BB% 99%E5%8F%B0%E5%B8%82%E8%8B%A5%E6%9E%97%E5%8C%BA%E5 %85%AD%E4%B8%81%E3%81%AE%E7%9B%AE%E8%A5%BF%E7%94%B A1-41&ie=UTF8&ll=38.253061,140.931609&spn=0.004145 ,0.007231&t=k&z=17&om=1
It's a bit like dancing, really. :)
My recollection's a bit fuzzy, but I seem to remember reading that all matter has "spin" to it. I put "spin" in quotes, as the sources I've read described it not so much as spin like what you get with a top, since elemental particles seem to approach true points, and therefore have no circumference that could spin around a center.
Anyway, I digress. The point I have is that everything has "spin". So does the anti-everything. If an electron has a spin of 1/2, then a positron would have the opposite of that -- or a spin of -1/2. This touches somewhat on the zero-sum idea, but as you've nicely pointed out, while the spins cancel, there is an awful lot of energy released.
As to why most things in this universe tend to spin one way and not the other (i.e. why we have more matter than antimatter), one idea I've run across is the notion that the universe itself has spin, thus establishing the bias.
For those more interested in spin as it pertains to particle and quantum mechanics, Wikipedia seems to have a decent article on the subject.
"What in the name of Fats Waller is that?"
"A four-foot prune."
Forgive me, but your post read a bit differently for me --
...flatulence. At least, that's what the "fondant filling" in those durn Cadbury Creme Eggs always does to me. :-o
"What in the name of Fats Waller is that?"
"A four-foot prune."
So no, the difference between matter and antimatter is not related the spin.
Hm, memory is clearly failing me somewhere. :) Is it the magnetic moment then that's opposite, like what's found between neutrons and antineutrons (http://en.wikipedia.org/wiki/Antineutron)? I have a distinct recollection that the difference between electrons and positrons is more than just reversed charge, or otherwise chargeless particle and anti-particle pairs like for neutrons wouldn't work...
"What in the name of Fats Waller is that?"
"A four-foot prune."
While this is venturing into areas where I'm much less experienced, I believe that the antiparticle is related to the particle through charge conjugation, which inverts all the internal properties of the particle (e.g. quarks->antiquarks). The site I linked has some more detailed info if you're interested.
Um...you got any better ideas of how to explain the empirical data? If not, then STFU.
First of all, I do not think there is anything wrong with being a dark-matter "agnostic". I applaud you for not believing in "highly theoretical proofs". I would not either. And I am not aware that physics can be understood through them. Physics is what we observe and the method of understanding that observation.
The problem I am still having problem conveying to you, I think is that 'dark matter' is not exactly a theory. It is rather a "solution" or "possible phenomena" that might be used to explain the observed results which have a high-statistics deviance from what we expect from the standard model of particle and astro physics. In some way, if you do not "believe" that the reason for such large deviations of observation from theory is not dark-*matter*-related but rather related to something else, such as *force* related, that's fine by me, I suppose. The problem with "messing" with forces rather than particles is that, well, forces effect quite a few things and so, you fix a problem but generall end up making another on the other side of the theoretical/observation universe.
My problem with the general public conception of dark matter or for that matter, most physical concepts, is that there is very little awareness of what is "observed" versus what is theorized. There are lots of astrophysical data that shows large deviations from what is expected. If you add in dark-matter, well, these deviations become trivial to explain. (No, the math there is really not *that* bad! Dont let people scare you -- if you are interested, try reading some papers.) The problem is that Nature is asking/forcing us to add something to the mixture. Dark matter, unlike Dark energy, was not cooked up by theorists, but rather forced on them, by experimental evidence. Now. maybe, just maybe, although very unlikely, there is another way to explain away the observed effects by changing how "forces" in nature act in some smart way. Again, I can not imagine how -- and yes, such theories require serious amounts of maths and ridiculous amounts of hand-waving to get around the problems they create while solving others!
The reason that so many people these days think that there is dark matter is that dark matter fits perfectly to the data from several astronomical epochs and from very different observational methods. The largest evidence comes from the CMB (Cosmic Microwave Background) which was when the universe was at about 300,000K so pretty young. Now, the supernova evidence which is higher by the day, spans through about half of the life of the universe. Observations are pushing back towards earlier and earlier times in the universe. The observed galactic rotational curves are from (approximately) current time of the universe. Thinkers of dark matter see that these nearly cover the whole 14 billion years of evolution of the universe and leave very little wiggle room for other theories.
Maybe you could say that dark matter has been hyped to give particle physicists something to discover at the LHC, the most expensive physics experiment to date. Certainly, if observed phenomena is due to dark matter, well, then LHC should discover the naughty particle which is at the heart of this. That would be a direct detection, but would than need further confirmation that this naughty particle is what accounts for a large fraction of the universe. Any experimental booklet will tell you that the first goal of the LHC is to find the Higgs and the next one is to find a dark matter candidate. If the LHC can find this particle, other observational particle physics experiments will have the further chance to change or tune their experiments to confirm that this is indeed true. So stay an agnostic! Hopefully, you will be convinced when and if the LHC discovers a particle which fits the bill... I am an experimental particle physicist working on an LHC experiment and I spend most of my time, thinking of how to find such a particle...
(and sorry about my English which sometimes fails me after a long and tiring day at work.)
Neutrinos effects (Their interaction with matter) were detected after they were predicted.
but in this case the dark matter is the theory used to 'justify' the results.
Also the other difference is that the neutrino interactions were detected in Earth, and is
repeatable in a controlled environment, while the dark matter effects are detected in faraway galaxies.
(which is what the GP is pointing out by asking for its detection in earth).
~561
Who cares 'where' it is? If it's true that the only known properties of dark matter are 'exterts gravitiy' and 'except for exerting gravitity it isn't at all like normal matter' then all you have is a crutch that adjustes a faulty models to fit observations. How much you can detail that crutch really doesn't matter if you can't answer the important questions like: what does this dark matter consist of? how does it react to normal matter? In short, what is this dark matter?
___
No power in the 'verse can stop me
A necessary first step in determining what something is made of is to first determine where it is. Last year, when the distribution of dark matter in colliding clusters was found, it helped us understand how "collisionless" the stuff is and what it might be (and what it couldn't be) made of. So far, what we know for sure is that it interacts gravitationally with other matter. We've got to know where it is and how it's distributed to find out more. Does it have any effect on light passing through it other than gravitation? We'd need to know if it is or isn't in the way of a distant galaxy to find out.
Actually the Earth radiates more energy than it gets from the Sun! The radioactive isotopes inside the Earth (along with tidal forces) give rise to heat, which keeps the Earth warm beneath the crust. This also (among other things) prevents the sea from sinking into the Earth.
I'm a physicist, though not a geo-physicist, so I apologize for the lack of detail.
Many falsifications in cosmology can be done much more cheaply on paper. We have a great deal of observational data which is taken to be real and physical. Hypotheses which make predictions of things we should see in current data but don't, are taken to be nonphysical. One branch of theoretical cosmology is applied mathematics that seeks out implications of hypotheses not initially understood by the people who initially advanced them, and this is used as a way of sorting out the not-yet-observed (maybe wrong) from the outright not-observed (wrong) predictions, and checking that the agreement between the hypothesis and observational data is correct.
There's nothing really called "dark matter theory" -- there is a hypothesis that unseen matter accounts for the curvature of spacetime on large structure scales (galaxies, groups of galaxies, The Great Wall, and so forth) that cannot be explained by visible matter. The nature of the unseen matter is also the subject of some speculation, and current work in the area is trying to arrive at a set of qualities it must possess in order to match our distant observations to the physical reality of our local environment.
The hardest problem is in the invisibility -- ordinary baryonic matter interacts with photons (scatter, absorption, reemission, and emission), whereas the unseen matter does none of this at any recognizable scale (and thus is called "dark").
At the scale of galaxies, dark matter is interesting because it does clearly deform spacetime, as does normal baryonic matter. The deformations, moreover, are not localized as they are in the case of stars -- the dark matter is diffuse, like a gas cloud. There is also observational evidence (from WMAP and Sloane) for the Lambda-CDM hypothesis, which holds that the dark matter is nonthermalized and collisionless, is at most dustlike in grain size, and is non-baryonic.
Experimental evidence (your "lab proof") requires a better understanding of the observed-in-the-sky qualities of dark matter, so that it can be related in terms of quantum mechanics, since QM people are already exploring interactions of normally-bound particles at energy levels that lead to differently-bound arrangements; taking advantage of this to would be efficient and practical. There is of course already work in this area, which is made a bit easier since Lambda-CDM proponents are by necessity gauge theorists as well.
Dark matter may be hadrons that are assembled in ways that do not experience the strong nuclear force. Alternatively, it may be bosonic in nature, either directly (Higgs) or through a light supersymmetrical partner. Many supersymmetry models have neutralinos as an emergent particle, and many of these could plausibly explain cold dark matter. Neutralinos are amenable to observation through their annihilations both in terms of gamma ray signatures and in terms of direct low temperature sensing in terrestrial equipment. There is also the somewhat related Axion hypothesis from QCD, which is undergoing in-lab testing using magnetic resonance microwave emission (to convert axions to its partner photons) and magnetic high-flux photon capture (which removes microwave photons from a mixed stream of such photons and axions). This work has already ruled out a range of properties with substantial observational implications incompatible with Lambda-CDM (for instance, axions cannot be partnered with photons with energies of microelectronvolt ranges).
There are even more exotic hypotheses, some of which resemble attempts to use GR as a unifying theory (from the Einstein-Rosen strong field deformation work). In essence, interactions currently studied in quantum mechanics can (possibly) be modeled using spacetime deformations, leaving gravity as the Grand Unifying Force. These scalar-tensor frameworks are awkward and make people nervous about name-calling, but s