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Dark Matter Found? $2 Billion Orbital Experiment Detects Hints

Soulskill posted 1 year,13 days | from the it-was-in-the-attic-this-whole-time dept.

ISS 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."

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173 comments

pertamax (-1)

Anonymous Coward | 1 year,13 days | (#43351601)

wow thats pretty expensive !

worth it, if... (2)

globaljustin (574257) | 1 year,13 days | (#43353247)

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...

Dark matter (1, Interesting)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43351653)

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:Dark matter (3, Funny)

Anonymous Coward | 1 year,13 days | (#43351663)

No.

Explanation (5, Informative)

Roger W Moore (538166) | 1 year,13 days | (#43353341)

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.

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:Explanation (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43353745)

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:Explanation (1)

Roger W Moore (538166) | 1 year,12 days | (#43354629)

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 - 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.

Re:Explanation (1)

Anonymous Coward | 1 year,12 days | (#43354129)

Why would Dark Matter be more diffuse? If it only interacts via gravity, shouldn't it be more compact than ordinary matter, with the only exception being black holes.

Re:Explanation (1)

50000BTU_barbecue (588132) | 1 year,12 days | (#43354467)

Well, without ionic or covalent chemical bonds (electromagnetics!), what do you think will happen? Gravity is a very weak force; you can charge up a party balloon with static electricity and it will stick on the ceiling, against the gravity of the entire planet.

Excellent Question! (5, Interesting)

Roger W Moore (538166) | 1 year,12 days | (#43354749)

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:Excellent Question! (0)

Anonymous Coward | 1 year,12 days | (#43355049)

So when a Dark Matter particle is attracted

What makes us believe dark matter is particulate?

Re:Dark matter (0)

Anonymous Coward | 1 year,13 days | (#43351703)

If it's intangible, how would you move/organize it to said highway?

Re:Dark matter (0)

Anonymous Coward | 1 year,13 days | (#43351777)

Gravity tractors. http://en.wikipedia.org/wiki/Gravity_tractor

Re:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43351779)

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:Dark matter (-1)

Anonymous Coward | 1 year,13 days | (#43351801)

Gravity works in both directions. If there is mass exerting gravitation to accelerate a ship toward its destination, there will still be mass exerting gravitation once the ships passes---except the ship would then be accelerated away from its destination.

That's on top of the chicken-and-egg problem of how are you going to move all that matter without shipping equipment across interstellar distances.

Go back to grade school and demand a refund.

Re:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43351839)

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 (4, Insightful)

lgw (121541) | 1 year,13 days | (#43352203)

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:Dark matter (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352267)

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.

Surely it can be created though, even if it can't be moved it should be something we can make, eventually. I'm obviously not settled on any of the details, just casting a net and seeing what flops up on deck. Stations generating a stream of the stuff off to the side? More practical than trying to catch antimatter pellets at near relativistic speeds, even if the energy needed to get refuelling lumps to that velocity didn't make the effort pointless.

Re:Dark matter (1)

wonkey_monkey (2592601) | 1 year,13 days | (#43352429)

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 (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352465)

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.

How do you know it would require incredible amounts of energy to generate dark matter? We aren't even sure what it is.

Re:Dark matter (0)

Anonymous Coward | 1 year,13 days | (#43352485)

Yet you are in full fantasy mode about sci-fi garbage. You seem to know what it is.

Re:Dark matter (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352629)

The parent post is a prime example of the kind of dunce that is more of a threat to scientific advancement than any creationist. If it doesn't already exist or is unlikely to happen in his lifetime, it's wild fantasy which no right thinking folk should countenance. He'd have run Jules Verne [wikipedia.org] out of town on a rail to appease his insecurities. Imagination is a primary ingredient in the development of our species.

Re:Dark matter (0)

Anonymous Coward | 1 year,12 days | (#43354517)

Well then why not suggest flying unicorns fed by maple syrup? Why is my idea any worse than yours?

Re:Dark matter (3, Informative)

lgw (121541) | 1 year,13 days | (#43352819)

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:Dark matter (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352883)

Yes but in the absence of a perfect 1:1 propulsion system using reaction mass, or anything even close to it, the question is could this possibly offer advantages. Of course the stars have relative velocities as well so any putative link between them would also have to be in motion.

Re:Dark matter (0)

Anonymous Coward | 1 year,13 days | (#43353111)

let the private sector do it once and charge a toll over a bizillion yearsm is that how its supposed to work?

Re:Dark matter (1)

idji (984038) | 1 year,13 days | (#43351885)

probably not, because you would have to expend energy to move the stuff around in to the position and density to do your bidding, perhaps a bit like moving a moon in front of your spaceship to be pulled along by its gravity, or perhaps like putting a big fan on a yacht to blow wind into the sails.

Re:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43351953)

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:Dark matter (1)

lgw (121541) | 1 year,13 days | (#43352917)

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:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352989)

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:Dark matter (1)

lgw (121541) | 1 year,13 days | (#43353123)

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:Dark matter (-1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43353145)

You've already made it abundantly clear that you've no idea what you're talking about, and I quote you directly, "Dark matter does not seem to form "structures" of any size." and are either unwilling or unable to grasp what I'm talking about, so stop wasting my time.

Re:Dark matter (0)

Anonymous Coward | 1 year,13 days | (#43353921)

You've already made it abundantly clear that you've no idea what you're talking about

As have you

Re:Dark matter (1)

The Raven (30575) | 1 year,13 days | (#43351987)

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 comparison.'

Re:Dark matter (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352029)

Once again, http://en.wikipedia.org/wiki/Gravity_assist [wikipedia.org]

You don't want a giant lump of gravity at either end, you want a trail of breadcrumbs between A and B. As for energy expended, while you're talking about an incorrect understanding of what I'm saying, a highway construction crew uses many times more energy and time than a car, but it makes the car's journey a lot more energy efficient, and there are dozens of orders of magnitude more cars on highways than there ever were construction crews.

Re:Dark matter (1)

Baloroth (2370816) | 1 year,13 days | (#43352123)

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:Dark matter (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352191)

The stars themselves are moving, if you wanted to build a connecting chain it would have to similarly move. The question I'm asking is would dark matter offer advantages in this regard... maybe a highway isn't the best description, a river perhaps?

Re:Dark matter (1)

wonkey_monkey (2592601) | 1 year,13 days | (#43352445)

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:Dark matter (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352503)

Maybe you missed this bit: "The question I'm asking is would dark matter offer advantages in this regard". If it can be generated or laid down in a way that is more efficient than blasting reaction mass out the back end of a spaceship, which wouldn't be difficult, it's worth consideration. Keep in mind I'm not making assertions here.

Re:Dark matter (1)

steelfood (895457) | 1 year,13 days | (#43352047)

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:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352083)

Your highway would have to be incredibly dense.

Or very very long, which handily enough describes the distances between the stars quite nicely.

Re:Dark matter (1)

dreamchaser (49529) | 1 year,12 days | (#43354221)

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:Dark matter (1)

tnk1 (899206) | 1 year,13 days | (#43352309)

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, it becomes easier to deal with. In essence, even if you need to spend a gigantic amount of energy to put say, planets in the right place, if you can do that in such a way that you can use a more efficient process to place them, you may make real gains on "normal" engines over the lifetime of the "highway". That's one reason why you might want some sort of propulsion system that instead uses energy to warp spacetime, as opposed to a rocket: you'll still need a crapton of energy, but it can probably be attained by something with a much higher energy density, like antimatter.

Note I am NOT suggesting that dark matter has anything to do with the above ideas. Like neutrinos, dark matter is so weakly interacting that you probably can't manipulate it usefully. In fact, some theories indicate that dark matter IS neutrinos, or neutrinos are a significant component of what is collectively considered "dark matter".

Re:Dark matter (3, Insightful)

wonkey_monkey (2592601) | 1 year,13 days | (#43352317)

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:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43352339)

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:Dark matter (-1)

Anonymous Coward | 1 year,13 days | (#43352565)

Interested in your child-like juvenile fantasy universe? Don't you already have psychiatric care at your facility?

Re:Dark matter (1)

lgw (121541) | 1 year,13 days | (#43352971)

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:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43353001)

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 velocities of stars, which I'll chalk up to me just not explaining the idea fully.

Re:Dark matter (2, Insightful)

lgw (121541) | 1 year,13 days | (#43353163)

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:Dark matter (0)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43353179)

Look, if you just want to ignore science, fine, believe whatever

That's rich coming from the guy that said dark matter didn't form structures. Again, spare your keyboard the wear and tear.

Re:Dark matter (2)

lgw (121541) | 1 year,13 days | (#43353251)

Ahh, I see adult conversation wasn't your goal in the first place. Fair enough.

Re:Dark matter (1)

Intrepid imaginaut (1970940) | 1 year,13 days | (#43353299)

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:Dark matter (0)

Anonymous Coward | 1 year,13 days | (#43352643)

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?

No, you're talking out your ass. Not only would your metaphorical highway be asinine if built the way you've described, but the property you've assumed would be helpful (not interacting electromagneticly) would be the single biggest hurdle to building the less asinine version out of dark matter instead of regular matter.

You could use a gravity tractor to propel a spaceship, but that doesn't actually gain you anything over just using whatever will propel your gravity tractor to propel the space ship directly.

You could place an artificial object or objects in orbits that are favorable for gravity assists, but conservation of momentum means that doing so would require you to put all the momentum gained by ships over the lifetime of the "highway" into the object up front for later use (plus it'll only be usable when the orbits align correctly). So again just attache that engine to your spaceship instead.

In both of those cases you want some massive object you can move with an engine of some sort. Since engines are made from baryonic matter they will not be capable of propelling a dark matter cloud. So even ignoring that they both end in "just attach the engine to your space ship it'll work better that way" you still can't use dark matter for any meaningful advantage.

But what is it? (5, Insightful)

Hatta (162192) | 1 year,13 days | (#43351661)

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:But what is it? (2)

brantondaveperson (1023687) | 1 year,13 days | (#43351723)

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? (5, Informative)

Anonymous Coward | 1 year,13 days | (#43351859)

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.

bad=best (1)

globaljustin (574257) | 1 year,13 days | (#43353161)

It seems you have a decent command of the subject, but your conclusion is wrong.

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.

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.

so Dark Matter is, by far, the best explanation.

Is this your scientific opinion? Yes/No...doesn't matter. Thanks for sharing. It's doesn't mean anything or contribute to the discussion in any way.

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.

Dark Matter theories are, IMSO, dumb. It doesn't matter why I say that for the purposes of my comment. What matters is, dumb as they are, they are the 'best fit'

Stop defending 'dark matter' theories like they are your children. They don't work, and will be replaced one day. I agree they are the 'best' but let's not confuse everyone over your need to be right with terminology ;)

Re:But what is it? (0)

Anonymous Coward | 1 year,13 days | (#43353887)

I recall a similar justification applied to epicycles.

Re:But what is it? (4, Insightful)

idontgno (624372) | 1 year,13 days | (#43352025)

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:But what is it? (1)

mbkennel (97636) | 1 year,13 days | (#43352311)

The luminiferous aether didn't have any observational or experimental evidence, and the theory was known to be problematic at the time.

Re:But what is it? (1)

Livius (318358) | 1 year,13 days | (#43352647)

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:But what is it? (1)

rknop (240417) | 1 year,13 days | (#43353351)

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 Matter, the theory has been tested, and it DID stand up.

Re:But what is it? (1)

steelfood (895457) | 1 year,13 days | (#43352127)

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:But what is it? (1)

Nadaka (224565) | 1 year,13 days | (#43351743)

And that is part of what this device attempts to answer.

The readings are consistent with the WIMP theory of dark matter.

Re:But what is it? (2)

wisnoskij (1206448) | 1 year,13 days | (#43351851)

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:But what is it? (0)

Anonymous Coward | 1 year,13 days | (#43352703)

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.

Re:But what is it? (1)

lgw (121541) | 1 year,13 days | (#43353025)

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? (5, Insightful)

lgw (121541) | 1 year,13 days | (#43351883)

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:But what is it? (1)

Hentes (2461350) | 1 year,13 days | (#43352093)

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:But what is it? (1)

MozeeToby (1163751) | 1 year,13 days | (#43352125)

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 energies of these electrons and positrons, we can start to narrow down exactly what kinds of particles actually make up dark matter

Re:But what is it? (2)

PolygamousRanchKid (1290638) | 1 year,13 days | (#43352479)

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:But what is it? (1)

Khashishi (775369) | 1 year,13 days | (#43352645)

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).

Wrong questions! (1)

Forty Two Tenfold (1134125) | 1 year,13 days | (#43353201)

It doesn't really, in strict sense, although one might by an honest mistake simplify it thus, exist, but rather, in a word, it is not non-existent. So to understand it better you have to exclude things it's not supposed to be diffrent from. I hope that clarifies things.

does it exist? (0)

Anonymous Coward | 1 year,13 days | (#43351719)

Yes, it exists. There really is no serious question about whether it exists. Its characteristics (hot, cold, individual mass, etc) are less certain, although it seems like there are some reasonably established constraints on some of those things too.

Anyway, there's also apparently not anything like a clear indication that this signal is a DM interaction => http://resonaances.blogspot.com/2013/04/first-results-of-ams-02.html

"However this is just a lot of smoke without fire. There's absolutely no way that measurements of the positron spectrum may give us a robust evidence for dark matter, not now, and not anytime soon. We simply have no robust way of telling dark matter from boring astrophysics in that channel, because we don't know the shape nor the normalization of the background. "

Don't you mean African-American matter? (-1)

Anonymous Coward | 1 year,13 days | (#43351735)

you insensitive clods

interesting first results...we'll see (5, Interesting)

ganv (881057) | 1 year,13 days | (#43351763)

That is a very interesting result. Their first measurements of the positron energy spectrum are consistent with super-symmetry ideas about dark matter collisions creating positron-electron pairs. If it turns out to be right, it will be the first non-gravitational detection of dark matter. But there is not much experimental support for the super-symmetry ideas being used to connect dark matter with positrons, and there are other possible sources of the positron spectrum at the current accuracy. So we'll see. It is great to see they have some results...this experiment has taken a long time and a lot of money. But when you introduce a much more precise way to measure, it usually turns out to be worth the cost and effort in the end.

Re: interesting first results...we'll see (0)

Anonymous Coward | 1 year,13 days | (#43352023)

I wonder if the discovery of electron/positron pairs emitted could possibly change the idea of the big bang... A sizable percent of the mass of the universe converting itself from what is essentially 'virtual' mass to real particles could suggest a slower, steadier creation.

Re:interesting first results...we'll see (3, Interesting)

TheRealMindChild (743925) | 1 year,13 days | (#43352059)

The Large Hadron Collider has more or less proved that Supersymmetry doesn't exist

Re:interesting first results...we'll see (0)

Anonymous Coward | 1 year,13 days | (#43353775)

Correction- the LHC has shown that supersymmetry does not likely exist at the energy scales tested.

Re:interesting first results...we'll see (3, Interesting)

DMUTPeregrine (612791) | 1 year,12 days | (#43354125)

Not even close to true. The LHC has shown that certain variants of supersymmetry can't exist, and shown nothing at all about other variants. Just because I didn't find my keys on my desk doesn't mean they haven't fallen between the couch cushions.

Spin? Not that type... (2, Informative)

Anonymous Coward | 1 year,13 days | (#43352163)

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?

Re:Spin? Not that type... (0)

Anonymous Coward | 1 year,12 days | (#43354175)

Don't remember much caution with regard to the FTL particles. There was skepticism from the outset.

What a load of crap... (-1)

Anonymous Coward | 1 year,13 days | (#43352423)

Dark Matter and Dark Energy are convenient fabrications designed by a cabal of charlatans to convince the public to continue to fund big science initiatives costing billions of dollars that do nothing more than offer hints that the charlatans may or may not be right. Modern physics has lost its way.

Physics! (0, Flamebait)

benjfowler (239527) | 1 year,13 days | (#43353395)

There's nothing like physics articles to bring out all the morons who think that because something is complex and counterintuitive, it's a license to make up any old bullshit they want.

And it's amazing how indignant the drooling retards get when they get called out on their bullshit by people who actually know what they're talking about (because they busted their arses at college for years, rather than just pulling shit out of their arses).

This is bullshit (4, Informative)

iris-n (1276146) | 1 year,13 days | (#43353449)

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:This is bullshit (1)

Kongming (448396) | 1 year,13 days | (#43353653)

While I'm not a physicist of any variety, the following text from the article also caused me to call its reliability into question:

"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:This is bullshit (1)

marcosdumay (620877) | 1 year,12 days | (#43354733)

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?

Yes, there is an old theory that can't explain a lot of recent observations.

Re:This is bullshit (1)

PvtVoid (1252388) | 1 year,12 days | (#43354275)

Wish I had some mod points to mod parent up. It's bang on.

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.

New Age idea (0)

Anonymous Coward | 1 year,13 days | (#43353593)

I have a great idea for a new religion or spiritual movement, following the concept that God lives in the gaps of our understanding.
Scientists will say that we don't meaningfully interact with dark matter, but one can just deny that and use it as the "explanation" for whatever mystical phenomena one wants to claim are out there. This will be hard (or even impossible, I believe) to disprove.
Auras? Dark energy. Souls? Dark matter. Et caetera.
I am too lazy, but this is Scientology-grade material and I think religious charlatans won't let it go to waste.
I'm just surprised they haven't done it already --- or maybe they have and I'm just not aware of it. In any case, the pathway to profit seems rather clear.
I have one firm prediction --- when they catch up with it, they'll claim that they knew about it all along, but they were just using a different language.
The same sort of claims are currently being made regarding the privileged role of the observer in quantum mechanics.

next to last (0)

Anonymous Coward | 1 year,13 days | (#43353709)

the penultimate shuttle mission to the orbital outpost.

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