Dark Matter Found? $2 Billion Orbital Experiment Detects Hints 173
astroengine writes "A $2 billion particle detector attached to the International Space Station has detected the potential signature of dark matter annihilation in the Cosmos, scientists have announced today. The Alpha Magnetic Spectrometer (AMS) was attached to the space station in May 2011 by space shuttle Endeavour — the second-to last shuttle mission to the orbital outpost. Since then, the AMS has been detecting electrons and positrons (the electron's anti-particle) originating from deep space and assessing their energies. By doing a tally of electrons and positrons, physicists hope the AMS will help to answer one of the most enduring mysteries in science: Does dark matter exist? And today, it looks like the answer is a cautious, yet exciting, affirmative."
Dark matter (Score:2, Interesting)
So if I have this right and someone please correct me if I don't, dark matter is transparent, we can see right through it, it's intangible and doesn't appear to interact with normal matter except through gravitational effects. Could such a thing be used to make some sort of dark matter highway to provide a gravity well between stars for ships to travel down without expending much energy?
Re: (Score:3, Funny)
Explanation (Score:5, Informative)
Second Dark Matter is incredibly diffuse, far more so than normal matter because it only interacts via gravity and - possibly - the weak force. So there it no way to make small, dense concentrations of it like you can with normal matter.
Finally, the AMS results does not yet show any evidence for Dark Matter. They need to extend their energy by a few bins to see whether the spectrum starts to drop - the current spectrum could be explained by pulsars - the positron excess has been known to be there for some years already thanks to PAMELA and Fermi/Glast(for a slightly more technical announcement with plots see here [web.cern.ch]). So it is a very interesting result but not yet evidence of Dark Matter. However, if it is Dark Matter, it should have a low enough mass to be created in the LHC so we may get a shot at finding whatever it is in 2015 when we turn back on with ~twice the energy. In fact my grad student and I worked on the ATLAS search for Dark Matter models associated with this type of positron-only signature but found no evidence. It's now being repeated with the 2012 data so stay tuned...
Re: (Score:2)
First the energy limit on interstellar travel is not getting out of the gravitational well of the sun it is getting up to a large fraction of the speed of light. If your intention was achieve that sort of velocity with a gravitational field then please try this is someone else's solar system because a gravitational field of that magnitude - think black hole - will do nasty things to planetary orbits.
Yes, if you read the rest of the comments the concept isn't within the solar system nor is it a single large gravitational field.
Second Dark Matter is incredibly diffuse, far more so than normal matter because it only interacts via gravity and - possibly - the weak force. So there it no way to make small, dense concentrations of it like you can with normal matter.
It does form structures, so I'd say it's too early to make definitive statements about what can and can't be done with it.
It's now being repeated with the 2012 data so stay tuned...
Will do.
Re: (Score:2)
It does form structures, so I'd say it's too early to make definitive statements about what can and can't be done with it.
That it does - huge, massive structures on a galactic and cosmic scale. The reason for this is that it interacts via gravity and, perhaps, the weak force. I agree that we can say very little about it at all at the moment but I do think that we can say that it will not form structures on a stellar scale which can generate a large enough gravitational field to accelerate an object to close to light speed in a reasonable length of time.
Yes, if you read the rest of the comments the concept isn't within the solar system nor is it a single large gravitational field.
You cannot stop a gravitational field at the edge of the solar system - g
Re: (Score:2)
That it does - huge, massive structures on a galactic and cosmic scale. The reason for this is that it interacts via gravity and, perhaps, the weak force. I agree that we can say very little about it at all at the moment but I do think that we can say that it will not form structures on a stellar scale which can generate a large enough gravitational field to accelerate an object to close to light speed in a reasonable length of time.
People are good at taking otherwise inoffensive substances and concentrating them into all sorts of volatile configurations. I'm not making any assertions, just blue skying it, but it's too early to say yea or nay at this point.
You cannot stop a gravitational field at the edge of the solar system - gravitational fields are infinite in extent. In order to have feasible interstellar travel you would need to have a reasonably rapid acceleration. Any gravitational field capable of generating that would disrupt planetary orbits.
Gravity gets stronger the closer you are to its source. A chain of dark matter 'planetoids' stretching between stars wouldn't have much of an effect on the endpoints, particularly since they wouldn't be in a straight line, or at least not that straight. The idea relies on small pushe
Physics (Score:2)
People are good at taking otherwise inoffensive substances and concentrating them into all sorts of volatile configurations.
Dark Matter is not made of atoms nor does it have any electrical charges. You cannot do chemistry with it - it is fundamentally different from any normal form of matter. What you propose is in direct contradiction to the know properties of Dark Matter.
Gravity gets stronger the closer you are to its source. A chain of dark matter 'planetoids' ...
Take a high school physics course and then do the maths. To get up to 10% of light speed (30,000 km/s), assuming your planetoid was Earth-sized and neglecting relativistic effects you would need a mass 22 times that of the sun. Now explain to me again how st
Re: (Score:2)
Dark Matter is not made of atoms nor does it have any electrical charges. You cannot do chemistry with it - it is fundamentally different from any normal form of matter. What you propose is in direct contradiction to the know properties of Dark Matter.
So you're saying it's impossible that science will ever be able to create the conditions to cause dark matter to come into being? It's a strange substance, not magical.
Take a high school physics course and then do the maths. To get up to 10% of light speed (30,000 km/s), assuming your planetoid was Earth-sized and neglecting relativistic effects you would need a mass 22 times that of the sun. Now explain to me again how sticking a mass 22 times larger than the sun anywhere near our solar system would not severely impair the orbits of the planets?
Twice as many would be needed because you have to slow down too. You don't aggregate the gravity on a single point because it's not in a single point, it is stretched over a half dozen light years. This is not a new concept, one variation is the Dyson Slingshot. The only question I'm wondering about is whether or not dark matter offers advant
Re: (Score:2)
Excellent Question! (Score:5, Interesting)
Why would Dark Matter be more diffuse? If it only interacts via gravity, shouldn't it be more compact than ordinary matter
That's a very intelligent question! That's exactly what you might expect but you need to go a little deeper. Think about a planet forming from a cloud of dust and rocks. Once a clump of a few rocks has formed it starts to pull in more dust and rocks from the surrounding cloud and a planet starts to form because rocks in the cloud are pulled in my the gravitational field of the clump until they smash into it and stop. This increases the mass of the clump so it pulls in more rocks and grows.
The critical part is that the only reason that the rocks stop when they hit the clump of material is because of the electromagnetic repulsion between the atoms in the rock and the atoms in the clump. This is the same reason that you do not fall to the centre of the Earth - the atoms on the soles of your feet are repelled by the atoms of whatever you are standing on.
Now lets think about Dark Matter. It has no electrical charge and so feels no electromagnetic force. So when a Dark Matter particle is attracted towards a clump of other Dark Matter particles it simply passes right through them without any interaction! It then starts to slow down under their gravitational field until it, eventually, turns around and flies back through the centre. Effectively all a "clump" of Dark Matter is is a group of particles oscillating back and forth in their shared gravitational well. This is why Dark Matter is so diffuse - it can form structures but only on a very large scale.
This is not quite the entire picture - there may be a very small chance of an interaction when Dark Matter particles pass by each other. This will help the particles to clump more but it will be a very, very slow process - and this is only the case if Dark Matter feels the weak force which is not certain. These interactions might also involve two Dark Matter particles annihilating which, if true, may give the positron signal which AMS sees. However to confirm this they need to look at a sightly higher energy which they claim they already have the data for.
Re: (Score:3)
What makes us believe dark matter is particulate?
It has a mass because it exerts a gravitational field and the distribution of the mass is non-uniform. This means it is a particle, unlike Dark Energy which is the energy of the vacuum.
Re: (Score:2)
This would result in huge sized, very diffuse clumps of Dark Matter. However all the data suggest that
Re: (Score:2)
Gosh. Another AC who - without reading the article - knows the true obvious answer that all those Nobel laureate were to dense to see.
If you bothered to read it you would see that the fact that positrons can be emitted by other sources is precisely why they are not calling this a signature of dark matter yet. You would also see that your "explanation" holds not a single drop of water - the positron flux detected is omnidirectional and does not vary with time ruling out any sources local to the solar syste
Re: (Score:2)
Re: (Score:2)
You'd have to expend energy anyway, rocket propulsion technologies of various sorts are pretty much laying down the highway in front of the car as they go, and ripping it up after themselves. While a highway construction crew might be a lot slower and more energy intensive than a car, they only do the job once and make it easier for all the cars that come after them.
What I'm wondering is, would the nature of dark matter lend advantages over any other material in terms of highway construction.
Re: (Score:2)
What I'm wondering is, would the nature of dark matter lend advantages over any other material in terms of highway construction.
From what we know: no, quite the reverse. Dark matter does not seem to form "structures" of any size. For normal matter, gravity + friction + entropy gives us clumping: atoms into molecules into dust into planets. That doesn't seem to happen with dark matter.
Re: (Score:2)
Eh, yes it does. http://en.wikipedia.org/wiki/Dark_matter#Structure_formation [wikipedia.org] There's even a nice picture of the dark matter structures.
Re: (Score:2)
Sigh. That's on the scale of galaxies and clusters, where gravity wins. Dark matter on the scale of stars is uncertain. That's not on the scale of a rocket, or a planet, which requires something other than gravity to keep bits stuck together - on that scale the evidence is there's no such force for Dark Matter. Below the scale of molecules, again, no evidence either way.
Re: (Score:2)
Sure thing, as soon as we can make a road that is downhill both ways. Since that is impossible, your idea is impossible. That is completely ignoring all other practical concerns such as 'if gravity can be felt light years away, it would alter the orbit of the sun' and 'if we could create something with measurable gravitational effects spanning light years between stars, then the amount of energy we expend accelerating and decelerating a spaceship is pretty puny (dozens of orders of magnitude puny) in compar
Re: (Score:2)
That is absolutely not how gravity assists work. Gravity assist work because the planet you are "assisting off" is moving: you can rob a little bit of that kinetic energy to give yourself a boost. But a "gravity highway"? No, you can't do that.
Re: (Score:2)
a river perhaps?
Implying that you've imparted momentum to the dark matter - momentum you may as well just impart directly to your spaceship.
Re: (Score:2, Insightful)
Re: (Score:2)
By all means point me in the direction of a better description of dark matter then.
Re: (Score:2)
Which Einstein showed didn't work the way some models of it assumed. And which quantum field theory brought back in spades.
Re: (Score:2)
Gravity is very, very weak. Your highway would have to be incredibly dense. And the amount of energy you're going to expend making that is probably better off spent ripping wormholes in the fabric of space and time.
Re: (Score:2)
Your highway would have to be incredibly dense.
Or very very long, which handily enough describes the distances between the stars quite nicely.
Re: (Score:2)
Your idea is just not feasible, for a lot of reasons people have tried to point out to you and that I won't bother repeating since you seem to keep ignoring them. It is a quaint and novel idea that might have a place in soft science fiction but for all those reasons already pointed out it just isn't workable based on our current understanding of physics, and isn't likely to be workable even in the far future.
Re: (Score:2)
I will say this: right now a great deal of the problem with rocket engines is that you have a reaction mass and throw it out the back to make the ship move in the direction you want. That means you generally have a low energy to weight ratio which makes accelerating/decelerating the ship much more difficult because you do have to carry around your road with you.
If you can find some way to manipulate the situation so that you don't have to carry that reaction mass around to get the needed velocity changes,
Re:Dark matter (Score:4, Insightful)
Could such a thing be used to make some sort of dark matter highway to provide a gravity well between stars for ships to travel down without expending much energy?
No more than it could be used to create a unicorn that poops cookie dough.
Re: (Score:2)
Thanks, that's very useful. I'll make sure there's a wikipedia entry for every comment I make henceforth and not throw out blue sky ideas for discussion among the interested.
Re: (Score:2)
You're throwing out fantastical ideas about stuff that is far outside of what might even be possible. That's not science, nor even science fiction (what might be possible one day): that's just fantasy. Not very interesting.
Re: (Score:2)
How would you know, you've already made two entirely false assertions, the first is the structure one, the second, well I'll quote another poster below: "No, dark matter contains more baggage than just embodying the discrepancy in galaxy rotation shear. For one thing, the title dark matter presumes that it is, in fact, matter. This is a different hypothesis than various modifications of gravitational force theories (which are not tenable now).". And this is aside from your misuderstanding about the relative
Re: (Score:3, Insightful)
Look, if you just want to ignore science, fine, believe whatever, but don't expect adult conversation. So far all you've said is "what if dark matter, instead of being what we think it is, were magic in this very convenient way?". Beyond that, did you have some coherent point to make?
Re: (Score:3)
Ahh, I see adult conversation wasn't your goal in the first place. Fair enough.
Re: (Score:2)
Two false assertions displaying complete ignorance of the topic, a couple of dollops of personal abuse, and a sprinkling of complete misunderstanding. Buh bye now.
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
You're insisting on misunderstanding the guy replying to you. There is evidence from multiple sources that dark matter cannot be ordinary (i.e. baryonic) matter.
Re: (Score:2)
Re: (Score:2)
There can never be "can only be" in science. But the evidence against dark matter being normal matter is pretty overwhelming. That hypothesis wasn't discarded lightly. If you go back about ten years there was a big debate about competing dark matter hypotheses, the MACHOs versus the WIMPs. MACHO is Massive Astrophysical Compact Halo Object, WIMP is Weakly Interacting Massive Particle. MACHOs are what you're describing - normal matter that's just too dark to see. WIMPs are something else.
The MACHO hypothesis
Re: (Score:2)
Re: (Score:2)
The strange thing about scientific communities is that they do consider all sorts of possibilities. Theoretical physicists in particular consider lots of things that they know are impossible just to see how theories work. Despite what you might read on Slashdot, baryonic dark matter, modifications to how gravity works on large scales and other dark matter hypothesis were certainly considered, over the last twenty years. That the WIMP dark matter hypothesis is the current leader isn't because it sounds li
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
I think it is something simpler: The "dark matter" would simply ordinary matter, but not detectable by us because it do not emit enough radiation and/or is not dense enough to block radiation.
Has been thought of. Has been tested. Empirical data shows that there is not enough non-radiative normal matter for it to be anything near dark matter. Via gravitational lensing and other large scale cosmological experiments, non-radiative matter has already been taken into account when studying other galaxies, and normal matter still comes up as only one sixth of the matter in the universe. All that was being done way back when they were trying to account for the rotational speeds of gravity. Since then, o
Re: (Score:2)
Re: (Score:2)
Shovel it off the back of a flatbed, obviously.
It has to have a process of creation, by the time we get to the stage of seriously contemplating interstellar voyages perhaps we will know how to make it, in the same way we can generate x-rays and similar.
Re: (Score:2)
http://en.wikipedia.org/wiki/Gravity_assist [wikipedia.org]
I'd rather move all that matter and equipment once to lay a trail than do it every time, even antimatter produces brutally poor returns over those kinds of distances.
Re:Dark matter (Score:5, Insightful)
Morbo says "Gravity Assist does not work that way!" Gravity assist uses a planet moving in the direction you want to go - you speed up by slowing down the planet. Energy is conserved.
You still have to expend the same energy to get to the same destination, if you have to put a moving planet there in the first place! Plus a bunch of overhead.
You gain little by being able to move through the planet - gravity assist works fine with normal planets.
Dark matter doesn't clump the way normal matter does (clumping requires friction, which is a very non-dark process): there's no obvious way to grab or move a bunch of it around. Think diffuse cloud of non-interacting particles.
Re: (Score:2)
Surely it can be created though
If it can, it would be at the expense of incredible amounts of energy, and the mass of the equipment and fuel required to generate the energy would probably outweigh the generated dark matter by billions of times. No free lunches in this universe.
Re:Dark matter (Score:4, Informative)
How do you know it would require incredible amounts of energy to generate dark matter? We aren't even sure what it is.
We are sure that it is dark. We are sure that it is matter. We are sure that matter and energy are collectively conserved. If it has mass, it requires E = mc^2 energy to create it.
Re: (Score:2)
The little that's known about dark matter is that it doesn't interact with normal matter (and only weakly at best with itself). That's a disadvantage, not an advantage, in any engineering scenario I can see. The hydrogen and oxygen interaction is exactly the sort of thing that dark matter doesn't do (as far as the minimal evidence known about it).
Maybe I'm not just imaginative enough around the engineering qualities of diffuse clouds, but there just doesn't seem to be any fodder for good science fiction i
Re: (Score:2)
Because we're assuming that creating dark matter isn't significantly different from creating non-dark matter?
Hint: Matter is not easily created.
But what is it? (Score:5, Insightful)
Of course dark matter exists. There's a discrepancy in our observations, and dark matter is defined as whatever is responsible for that discrepancy. The real question is, what is dark matter? How do we explain its existence?
Re: (Score:3)
Unless the responsibility for the discrepancy falls upon incorrect theories / understanding of the observations. In which case dark matter turns out to be an iffy equation. Yes, it still technically exists, but the $2 billion dollar particle detector isn't going to find it.
Re:But what is it? (Score:5, Informative)
Unless the responsibility for the discrepancy falls upon incorrect theories / understanding of the observations. In which case dark matter turns out to be an iffy equation. Yes, it still technically exists, but the $2 billion dollar particle detector isn't going to find it.
We can say, with a very high degree of uncertainty, that the discrepancies are not due to bad theories.
If our only line of reasoning for Dark Matter was Newtonian physics (for example, if the only evidence for Dark Matter was from rotation curves of galaxies), your thought would be entirely reasonable. Maybe Newtonian mechanics were just wrong on the scale of galaxies. This is one reason why Modified Newtonian Dynamics theories (MoND) were somewhat popular a while ago.
But the problem is that multiple, *completely independent*, physical theories all show that not only does Dark Matter exist, but all the theories predict consistent amounts of Dark Matter. For example, you can use Einstein's Theory of General Relativity to find out how much Dark Matter there is based on how much light is curved by gravitational effects. Or you can use various areas of Thermodynamics to look at temperatures in galaxy clusters.
These theories are based on completely different principles and laws. Yet they all predict the same thing.
So if you want to claim that we being confused by bad theories, you would have to be able to explain why multiple, completely independent theories are not only all wrong, but all wrong in a way such that they return the same wrong answer. That seems extremely implausible, so Dark Matter is, by far, the best explanation.
Re: (Score:3)
with a very high degree of uncertainty
Gotcha!
*ducks*
bad=best (Score:2)
It seems you have a decent command of the subject, but your conclusion is wrong.
Because they are trying to 'fill' the same gap in observed matter! Please, you must see the fallacy of your argument here. They start with the problem: we observe X but our *really good* calcula
Re: (Score:2)
Because they are trying to 'fill' the same gap in observed matter! Please, you must see the fallacy of your argument here. They start with the problem: we observe X but our *really good* calculations say it should be Y. Y-X=ammount any theory will have to account for.
No, the start is a step back from that: Starting with very different theories whose effects we can observe on earth, and expanding the theories to the galaxy or universe domain, they all give the same roughly/exactly the same Y. The simplest answer is that they all fail to take into account the same amount of matter, not that they all just happen to be wrong in just the right way to trick us.
In science, the 'best fit' theory is shorthand for saying the theory that doesn't solve a problem completely, but by consensus represents the best our human ability can offer in solving that problem at that time in history.
That is a description of all of science. It never gives us ultimate answers, just better and better approximations o
Re:But what is it? (Score:5, Insightful)
Like luminiferous aether [wikipedia.org] existed until it didn't [wikipedia.org].
That said, these particle detections seem analogous to if Morley and Michelson had detected discrepancies in the speed of light attributable to earth's motion through the universe (and therefore relative to the aether). They didn't and the aether theory began to be disproved
In this case, the theoretical construct (dark matter) is beginning be supported by experimental observations, rather than disproved. So dark matter continues to be a useful concept, even if we're not sure what its tangible form of existence is.
Re: (Score:2)
The luminiferous aether didn't have any observational or experimental evidence, and the theory was known to be problematic at the time.
Re: (Score:2)
Like luminiferous aether [wikipedia.org] existed until it didn't [wikipedia.org].
And then it did again. Space-time has curvature and energy - that sure isn't the classical meaning 'empty' space. The aether just wasn't material in the sense it was originally conceived.
Similarly, dark matter is *something* which is explaining a wide variety of observed phenomena with several limits on what it could possibly be. The name is just a matter of labelling.
Re: (Score:2)
Dark Matter is not like the luminiferous aether. That was the title of a podcast I made three years ago -- here it is: http://cosmoquest.org/blog/365daysofastronomy/2010/06/26/june-26th-dark-matter-not-like-the-luminiferous-ether/ [cosmoquest.org]
The luminiferous aether was a theory developed to explain a discrepancy... as was dark matter. The difference is, there are LOTS of different lines of evidence to point towards dark matter. With the luminiferous aether, the theory was tested, and it didn't stand up. With Dark M
Re: (Score:2)
That's not even the real story. There were lots of different aether theories (and lots of dark matter theories). Some predicted Michelson and Morely's result, some the opposite. The latter were disproved. The former weren't, but kind of got ignored when everyone got distracted by shiny relativity (never mind that general relativity is most commonly explained in terms of gravitonic aether - i.e. distorted spacetime). Then quantum field theory came along and now we all believe in many kinds of aether, but we
Re: (Score:2)
Dark matter only accounts for around 30% of the universe's mass. It's gravitational effects are visible, so we're pretty sure it exists in some form or another. It could be a new subatomic particle. It could even be existing bayronic matter that's masked by some advanced alien technology. But it has been observed to exist.
Dark energy, which makes up the rest of the mass in the universe, is where the alternate ideas based on our incomplete understanding of subatomic physics is possible.
Re: (Score:2)
It could even be existing bayronic matter that's masked by some advanced alien technology.
If there were enough baryonic matter in the universe to account for the dark matter as well, the ratios products of big bang nucleosynthesis would be different than what we observe.
Re: (Score:2)
Re: (Score:2)
And that is part of what this device attempts to answer.
The readings are consistent with the WIMP theory of dark matter.
Re: (Score:3)
I disagree. Dark Matter is defined as one possible specific solution to this discrepancy.
Specifically:
It has to be matter.
It has to be made up of particles.
It has to be invisible.
It has to make up most of the matter of our universe.
If it did not at least meet all of these criteria, Dark Matter would not exist.
Re: (Score:2)
If we considered gravity not as a property of matter, but as a phenomena associated with the packet of energy that a mass represents... If that were the case, then in theory - regions of space with high enough energy density (but no matter) would also produce gravitational effects.
Maybe somebody should work from that angle and see if dark matter still holds up.
The cosmic microwave background radiation studies debunked that idea. We can now divide "gravitational effects" cleanly into 3 buckets: "normal" matter, "dark" matter, and energy. The ratio of normal/dark matter that was predicted from galactic rotation was in fact observed by the CMBR studies.
Re:But what is it? (Score:5, Insightful)
Of course dark matter exists. There's a discrepancy in our observations, and dark matter is defined as whatever is responsible for that discrepancy
To clarify: the "dark matter" hypothesis of the discrepancy in our observations of galaxy (and cluster) rotation rates has already been confirmed by observations of the cosmic microwave background radiation. There were many hypotheses for that discrepancy, but dark matter predicted the correct ratio of baryonic/non-baryonic matter in the early universe - to multiple significant digits (rare in cosmology).
So while most properties of dark matter have yet to be understood, some are well defined. As far as "how do we explain its existence?", that same question applies equally to "normal" matter.
Re: (Score:2)
Theories trying to explain gravitational anomalies can be classified in two categories, dark matter theories and modified gravity law theories. Furthermore, the measurements of this experiment can be explained by WIMPs, which is a specific dark matter theory.
Re: (Score:2)
There are other possible ways to explain the effects than dark matter. The evidence has slowly been building that dark matter is the best explanation, but at one point modifications to our understanding of gravity was also considered. This data adds another piece of evidence that there is mass floating out there that we don't understand, as opposed to there being a term missing from our equations. More interesting, since we've been pretty sure dark matter is the answer for a while now, if they know the e
Re: (Score:3)
I think this is best explained with a computer analogy, using the concepts of real and virtual:
If it's there, and you can see it, it's real.
If it's not there, but you can see it, it's virtual.
If it's there, but you can't see it, it's Dark Matter.
If it's not there, and you can't see it, it's gone.
Re: (Score:2)
No, dark matter contains more baggage than just embodying the discrepancy in galaxy rotation shear. For one thing, the title dark matter presumes that it is, in fact, matter. This is a different hypothesis than various modifications of gravitational force theories (which are not tenable now).
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
interesting first results...we'll see (Score:5, Interesting)
Re:interesting first results...we'll see (Score:4, Interesting)
Re:interesting first results...we'll see (Score:4, Interesting)
Spin? Not that type... (Score:2, Informative)
A contrary opinion: http://profmattstrassler.com/2013/04/03/ams-presents-some-first-results/
It's always good to exercise caution with these sorts of things. You all remember the FTL particles a couple years back yes?
This is bullshit (Score:5, Informative)
As usual, this is just a press release full of hype.
They didn't discover dark matter. They measured, with higher precision than ever, the excess in the positron fraction coming from cosmic rays. The existence of this effect, however, was already well-established. The question that was open, and still is, is which is the origin of this effect. One of the possible answers is dark matter. The problem with this answer is that we have to assume a discredited theory -- supersymmetry, and even within this theory a very artificial model of dark matter annihilation. The higher precision of the current measurements does not credence to this answer, nor does it discard more boring answers (i.e. coming from astrophysical processes that do not involve new physics). If you want to understand more about it, please read it from an actual particle physicist [blogspot.co.at]. I am a physicist, but not an astrophysicist nor a particle physicist.
Please keep in mind that I'm not criticising the AMS experiment itself: its job was to measure this excess with high precision, and this it did quite well. What I'm criticising is the people who have published this irresponsible press release.
Re: (Score:2)
"As the moniker suggests, dark matter is dark; it doesn’t interact with electromagnetic radiation."
Isn't one theory that dark matter is normal baryonic matter, just not baryonic matter that is concentrated or luminous enough to have a measurable effect on any light getting to us?
Re: (Score:2)
Yes, there is an old theory that can't explain a lot of recent observations.
Re: (Score:2)
Sorry, this is not the case. Again, I'm not an expert on this, but the best evidence I now that dark matter isn't just normal matter that happens to be dark is the Bullet Cluster [wikipedia.org]. The thing is that, even if we can't see the normal matter, we know that it interacts with normal matter, well, normally. So in a collision of galactical clusters, we expect even this dark gas to interact a bit and get left behind, while the interactionless dark matter passes straight throught, and this is what we have observed in
Re: (Score:2)
Theory? (Score:2)
I think you mean "hypothesis". Yes, scientists get carried away with calling their wacky unsupported ideas "theories".
Re: (Score:2)
AMS confirmed (to much higher precision) the excess already observed by PAMELA [wikipedia.org] and Fermi [stanford.edu]. This is interesting. It is also a long way from even an indirect detection of dark matter. Meanwhile, there is no evidence for SUSY [scientificamerican.com]. None. Nada.
Bullshit (Score:2)
What widely accepted model of particle physics predicts this? Right, NONE.
Ridiculous (Score:2)
P.S. I still think dark matter is a fantasy created from bad math.
mixing up proof and evidence again (Score:2)
worth it, if... (Score:3)
the data can disprove 'Dark Matter' theories...
that's worth $2 Billion in my mind...
Loop Quantum Gravity [wikipedia.org] is by far a more elegant theory. The only problem is Cambridge really...they like their multi-verse theory a little too much over there...
Re: (Score:2)
the data can disprove 'Dark Matter' theories...
that's worth $2 Billion in my mind...
Loop Quantum Gravity [wikipedia.org] is by far a more elegant theory. The only problem is Cambridge really...they like their multi-verse theory a little too much over there...
If only LQG said anything about dark matter then you might get your wish.
Re: (Score:2)
Re: (Score:2)
Well, it required a shuttle launch to get it up there. That's a good part of the price tag. Usually these things include the science for a few years as well. And it is a complicated piece of high precision electromechanical hardware. In orbit.