Dark Matter Discovered Near Solar System?

gpronger writes "The ATIC (Advanced Thin Ionization Calorimeter) has potentially discovered the presence of dark matter close (only 3000 light-years) to our solar system. The system detected a large-amount of high energy cosmic rays which match the theoretical signature of dark matter annihilating itself. The universe is believed to be composed of about 25% dark matter, but there has been little evidence of it. This discovery, if correct, would be the first." The paper was published in Nature , but it requires a subscription to see beyond the abstract.

Comments

In Soviet Russia

[wideBlueSkies]

Dark Matter sees evidence of YOU.

zomg

[Missing_dc]

ZOMG, Mom, is that you?

Re:zomg

[Missing_dc]

see http://www.xkcd.com/502/ for the joke

Re:zomg

[Hurricane78]

*ROFL* Parent is definitely on topic and underrated. See the xkcd link above.

Re:zomg

[Anonymous Coward]

xkcd: usually very funny, sometimes very sad

Re:zomg

[Anonymous Coward]

If that's informative on Slashdot, a lot of people need to hand in their geek cards.

Re:zomg

[Anonymous Coward]

lame as hell, think for yourself

math hosers.

[shentino]

> What's more, the signal peaked at 650 GeV and then rapidly declined to the background level at
> 800 GeV.

Uh...

Peaking at 650G and then declining to 800G?

Did TFA just royally f**k up its math or something?

Re:math hosers.

[blueg3]

You have a background intensity that is a function of energy, B(E).

Signal intensity is also a function of energy, S(E).

The observed intensity I(E) is B(E) + S(E). The signal portion (observed intensity above background level) peaks at E = 650 GeV. At 800 GeV (and, one would assume, higher), the signal is small enough that the observed intensity is adequately explained only by background.

Re:math hosers.

[slashdotlurker]

No.
They have an energy dependent signal.

Re:math hosers.

[arminw]

...They have an energy dependent signal....

So there is a signal, but what produces it is still only a conjectural speculative interpretation of an observation. From experiments here at home, such radiation is ONLY and ALWAYS produced by charged particles. Instead of dark matter, the radiation could be produced by naturally occurring interstellar or intergalactic particle acceleration. It could even be some space alien's giant version of the LHC. All we observe is lots of radiation, but then they are guessing what produces it. If it is dark matter, then there should also be dark antimatter.

We know from measurements that the sun produces or is involved with an enormous amount of electrical current we call the solar wind. Even though the earth intercepts only a minute fraction of this, some strong outburst of solar electricity has shut down power grids and communication systems.

Even if there is an interstellar electric field of only millvolts per kilometer, the vast distances of space can still accelerate charged particles, mostly electrons, to immense energies. These could produce much radiation when they encounter intense magnetic fields we have observed. Annihilation of any sort is only one other, far less likely possibility.

Re:math hosers.

[Anonymous Coward]

It's dark matter, so it's upside down.

Re:math hosers.

[Egdiroh]

The graph of -(x - 3)^2 + 5 peaks at 3 but rapidly declines bellow by 6

. You are assuming that the numbers were the range of the observations not the domain. that's why is said at 650 GeV not to 650 GeV.

Re:math hosers.

[Deadstick]

Did TFA just royally f**k up its math or something?

No, their math is just peachy.

A figure like 650 GeV is the energy of ONE cosmic ray. Think of a graph of the number of rays arriving per second versus the energy of the individual rays. You're getting this many 400 GeV rays per second, this many 500 GeV rays, and so on.

What TFA says is that LOTS of 650 GeV rays were arriving from the newly observed source, and hardly any 800 GeV rays except for the background rate that you get from everywhere in the sky.

rj

Re:math hosers.

[blueg3]

I think I've seen you make this comment before.

As before, this radiation is not solely produced by charged particles.

Re:math hosers.

[arminw]

...As before, this radiation is not solely produced by charged particles.

What other KNOWN way is there to produce ELECTROmagnetic radiation, except with electrons? What other way is there to produce a magnetic field besides and electric current?

Re:math hosers.

[sootman]

In defense of the parent, math with dark matter can be hard. Dark matter is so dense, each pound of it weighs over ten thousand pounds!

Re:math hosers.

[CTachyon]

Dude, seriously, read up on electroweak theory. You're so 1960's.

Re:math hosers.

[ceoyoyo]

http://en.wikipedia.org/wiki/Technetium-99m

There are lots of reactions that produce EM radiation. This one is used in medical imaging. Positron-electron annihilation also creates gamma rays. Yes, those are charged particles, but the gammas are not produced by the charges moving. That reaction is also used every day in medical imaging.

All these resources available on the Internet and you can't even educate yourself. Such a waste.

Re:math hosers.

[Ambitwistor]

I can't get past the paywall to see how many sigmas they put on the detection event, but I seriously doubt the situation is as simple as you claim. I personally find it unlikely they would get published in Nature with a signal that is statistically indistinguishable from background noise. Unfortunately, I can't read the paper to see what they did. I'm not a particle astrophysicist, but you don't mention at all what the error bars are; a 150 GeV difference can be big or small depending on how precise the measurement is. The location of the peak is also not the only factor which you can use in detection; the height and shape of the I(E) curve matters, as well as the time signature (light curve). Quite possibly they found a real source. Whether that source is dark matter is another issue.

Re:math hosers.

[niklask]

Not only is he 1960's, he's a troll from the 60's. No need to feed the trolls.

Re:math hosers.

[Deadstick]

Sure, but Nibbler doesn't care about the math.

rj

Re:math hosers.

[Goaway]

Uh, annihilation radiation? Radioactive decay? They're pretty well known.

Re:math hosers.

[budgenator]

Peaking at 650G and then declining to 800G?

Did TFA just royally f**k up its math or something?

The Author's assume that a reader of the article would be scientifically astute enough to realize that were referring to the number of detections over a spectrum of energies; in your case they were overly optimistic.

Re:math hosers.

[arminw]

...electroweak theory....

So now tell me where the ELECTRO part of this comes in? Does that not come from electron? What is an electron? Does it have a charge? What happens if that charge moves, specifically is accelerated as it flies out of a decaying atom and runs into something, like another atom or a magnetic field produced by other moving electrons? Has what happens in an atom that decays by this electroweak interaction changed since the 1960s or did it not exist before then? Obviously, electroweak is included in the operation of the ENTIRE universe. The laws of physics operate in the same manner here at home and in the most distant galaxy.

Re:math hosers.

[blueg3]

I'm not sure I understand your reply. Did you read the parent post? I was just explaining that their signal is I(E). The wording of the summary was confusing some people.

You are correct, though -- it's highly unlikely they'd be published in Nature without having a statistically significant deviation from background. They'd at the very least need to have found a real source, and they'd have to have a good argument that that source is dark matter.

Re:math hosers.

[budgenator]

What other KNOWN way is there to produce ELECTROmagnetic radiation, except with electrons? What other way is there to produce a magnetic field besides and electric current?

How about spinning atomic nucleus, alpha radiation or proton beams? In solid state electronics holes are common carriers of electromagnetic force, the holes are actually missing electrons so they are essentially nothing! Just about anything involving gamma ray photons have more energy than can be produce by electron/positrons.

Re:math hosers.

[Ambitwistor]

I think I misunderstood your argument. I thought you were saying that a peak at 650 GeV is statistically indistinguishable from a background peak at 800 GeV. After re-reading it a couple of times, it looks like you're saying that the signal is distinguishable from background at 650 GeV where it peaks, but not at 800 GeV.

Re:math hosers.

[budgenator]

what is an electron?
Long Answer; It's a thingy with a specific rest mass, a specific charge, a specific spin and when you smack it really hard it breaks into reasonable predictable pieces that don't look much like the original thingy called an electron.
Short Answer; We don't have a clue but we delude ourselves into thinking we know more than we do.

Re:math hosers.

[budgenator]

how do you weigh out a pound that weighs ten thousand pound?

Re:math hosers.

[niklask]

...electroweak theory....

So now tell me where the ELECTRO part of this comes in? Does that not come from electron?

No. It comes from electric charge. Its not just electrons that have electric charge. Geez, read some physics.

What is an electron? Does it have a charge? What happens if that charge moves, specifically is accelerated as it flies out of a decaying atom and runs into something, like another atom or a magnetic field produced by other moving electrons? Has what happens in an atom that decays by this electroweak interaction changed since the 1960s or did it not exist before then? Obviously, electroweak is included in the operation of the ENTIRE universe. The laws of physics operate in the same manner here at home and in the most distant galaxy.

How do you know that they are the same here and in the far corners of the Universe. Short answer is: you don't. Its an assumption we make.

Re:math hosers.

[blueg3]

Correct. That's what the article is saying -- it peaks at 650 GeV, and by 800 GeV is indistinguishable from background.

Re:math hosers.

[arminw]

...How do you know that they are the same here and in the far corners of the Universe...

We have observational evidence carried by the radiations from the distant regions of the universe, that rules of electricity and atomic behavior is as it is in your backyard.

(...No. It comes from electric charge..)

Technically you are of course right. The word electron comes from the Greek word for "amber" because they observed that a piece of amber, when rubbed would attract small particles. Any time a charge is accelerated photons are produced.

Re:math hosers.

[niklask]

...How do you know that they are the same here and in the far corners of the Universe...

We have observational evidence carried by the radiations from the distant regions of the universe, that rules of electricity and atomic behavior is as it is in your backyard.

(...No. It comes from electric charge..)

Now you are using the same arguments that yo say are wrong in the case of dark matter. Stop contradicting yourself.

Technically you are of course right. The word electron comes from the Greek word for "amber" because they observed that a piece of amber, when rubbed would attract small particles. Any time a charge is accelerated photons are produced.

While true, this is not the ONLY source of high-energy photons, which you claim.

Re:math hosers.

[arminw]

...While true, this is not the ONLY source of high-energy photons,...

Beside than an accelerating charge, what other source of electromagnetic radiation is there that we know of?

Re:math hosers.

[Anonymous Coward]

Beside than an accelerating charge, what other source of electromagnetic radiation is there that we know of?

Jesus, you really are ineducable, aren't you?

This whole thread is about sources of EM radiation other than accelerating charges. One example is matter-antimatter annihilation, which you persistently and incorrectly dismiss as an example of charge acceleration.

Re:math hosers.

[niklask]

Direct production in hadronic interactions. Decay of neutral pions. Seriously, you need to catch up with physics.

Re:math hosers.

[arminw]

...Seriously, you need to catch up with physics....

From Wikipedia:

"Electron-positron annihilation occurs when an electron and a positron (the electron's anti-particle) collide. The result of the collision is the conversion of the electron and positron and the creation of gamma ray photons or, less often, other particles. The process must satisfy a number of conservation laws, including:
Conservation of charge. The net charge before and after is zero.
Conservation of linear momentum and total energy. This forbids the creation of a single gamma ray.
Conservation of angular momentum.
As with any two charged objects, electrons and positrons may also interact with each other without annihilating, in general by elastic scattering."

http://en.wikipedia.org/wiki/Pions

Neutral pion decays
The 0 meson has a slightly smaller mass of 135.0 MeV/c2 and a much shorter mean life of 8.4×1017 seconds. It decays due to electromagnetic force. The main decay mode (98.798%) is into two photons...

Still, positrons and electrons are CHARGED objects which are accelerated as they collide. Their charges cancel out and the energy is carried away in ELECTROmagnetic radiation. The electric interaction, NOT gravity nor the strong nuclear force are involved. ANYTIME and ALWAYS, when photons are produced, since they are a phenomenon of the ELECTRIC interaction, they come from a charged object in accelerating motion.

A neutral pion decays "due to electromagnetic force."

Therefore, electrical charge interaction is the source of the radiation observed. Fictional dark matter need not apply. The same goes for black holes, neutron stars and other esoteric objects theorized to exist in galaxies far, far away, but nowhere around here, closer to home. All those objects and constructs are modern scientific fairy tales fit for a Star-Wars movie. The Universe operates by a combination of well tested electrical and gravitational laws. Every single actual observation we make, can be adequately explained by their operation. Present cosmological theories, as beautiful mathematically they may be, are obviously in need of serious revision. Making the observed data fit a theory is NOT science, but the theory must fit the data.

That was my original point.

Re:math hosers.

[niklask]

You do not have to copy-paste Wikipedia articles. Links are just fine. (And btw, I am a particle physicist.)

Still, positrons and electrons are CHARGED objects which are accelerated as they collide. Their charges cancel out and the energy is carried away in ELECTROmagnetic radiation. The electric interaction, NOT gravity nor the strong nuclear force are involved.

Pion decay is NOT due to accelerating charges. Pions decay even at REST.

ANYTIME and ALWAYS

Plain wrong. Ask any particle physicist about direct production of photons in hadronic interactions.

when photons are produced, since they are a phenomenon of the ELECTRIC interaction, they come from a charged object in accelerating motion.

Now you are contradicting yourself again. Photons from neutral pion decays do not come from "accelerating motion".

A neutral pion decays "due to electromagnetic force."

Still has nothing to do with acceleration.

Therefore, electrical charge interaction is the source of the radiation observed. Fictional dark matter need not apply. The same goes for black holes, neutron stars and other esoteric objects theorized to exist in galaxies far, far away, but nowhere around here, closer to home.

You need to check in with modern observations.

All those objects and constructs are modern scientific fairy tales fit for a Star-Wars movie.

Sadly for you, your story is even worse.

The Universe operates by a combination of well tested electrical and gravitational laws.

And fittingly you leave out strong interactions. You are just plain laughable.

Every single actual observation we make, can be adequately explained by their operation.

It is sad that you do not realize this is self-contradictory. Here you say that it can be fully explained, but below you say we have to revise the math.

Present cosmological theories, as beautiful mathematically they may be, are obviously in need of serious revision.

There are, as has been pointed out before to you but you refuse to listen, two options: 1) missing matter 2) incorrect gravitational theory. Option 2 is far less likely because of the extreme accuracy of relativity in other scenarios.

Making the observed data fit a theory is NOT science, but the theory must fit the data.

That was my original point.

Have you ever read about the history of the neutrino? Please do so! And since you obviously do not understand how the scientific model works, I rest my case.

Re:math hosers.

[arminw]

.. two options: 1) missing matter 2) incorrect gravitational theory...

How about option 3) electrical discharges as part of powerful magnetic and electric fields?

(...And fittingly you leave out strong interactions...)

The strong interaction is not DIRECTLY observable to us, because of the fact that it operates over only very short distances. At cosmic distances we only directly observe the electric force through photons we intercept. We also observe thorough photons the gravitational (inertial) force in how it governs the motions of heavenly bodies. Gravity waves are theorized to exist, but there has so far been no success of detecting or measuring them. Maybe they do exist, but there is no evidence, so far, that they do.

I think we are not really disagreeing, but have a misunderstanding of terms.

Much of present mainstream cosmology is based on two underlying assumptions. 1) That the observed red-shift of distant objects is due to motion (doppler effect) and 2) that gravity alone determines the structure and behavior of the large scale universe. I think that modern data does not support these assumptions. It is not an understanding of atomic physics that is at issue here.

If those two assumptions are tossed, then all the fairy tale cosmological constructs fall away and well understood electrodynamic processes can adequately explain all the actual data we observe.

Food for thought: If there is a pervasive electrical field in space, analogous to the cosmic background radiation, could that explain the incredible energies we measure in cosmic rays? If there is an such an electric field of only a few micro-volts per meter, could such a field accelerate a charged particle to the energies we observe? We could never directly measure such a small electric field.

Space probe data indicates that the energy of the electrons of the solar wind INCREASES slightly as they get further away from the sun. That means the existence of an accelerating force. There may be localized regions in space with vastly greater fields. Could these fields not accelerate electrons and other charged particles to high energies? If these high energy electrons then get deflected by the magnetic fields known to exist around stars and planets, would they not also emit plenty of synchrotron radiation which we have interpreted as evidence for black holes? Furthermore, do we know of a way of generating a magnetic field without an electric current or more correctly, the movement of charge?

Re:math hosers.

[niklask]

.. two options: 1) missing matter 2) incorrect gravitational theory...

How about option 3) electrical discharges as part of powerful magnetic and electric fields?

No, electric charge does not give rise to mass nor interact gravitationally.

(...And fittingly you leave out strong interactions...)

The strong interaction is not DIRECTLY observable to us, because of the fact that it operates over only very short distances.

Again, particle physicists around the world disagree with you, strongly!

At cosmic distances we only directly observe the electric force through photons we intercept.

Again, this is based on your misconception about what produces photons. And again, its electroweak, not electric interaction.

We also observe thorough photons the gravitational (inertial) force in how it governs the motions of heavenly bodies.

Gravitational mass and inertial mass are two different things. Gravitational interaction does not produce photons.

Gravity waves are theorized to exist, but there has so far been no success of detecting or measuring them. Maybe they do exist, but there is no evidence, so far, that they do.

Correct. Interesting how you can accept the hypothesis of gravitational waves, which is a consequence of relativity theory, which you on the other hand have dismissed when saying that there are no black holes and cosmology is wrong.

I think we are not really disagreeing,

Oh yes we are, as is most of the community.

but have a misunderstanding of terms.

No. But you have a misunderstanding of physics as it stands today.

Much of present mainstream cosmology is based on two underlying assumptions. 1) That the observed red-shift of distant objects is due to motion (doppler effect)

Cosmological red shift is not the same as the Doppler effect

and 2) that gravity alone determines the structure and behavior of the large scale universe. I think that modern data does not support these assumptions.

Which is because you do not understand the data.

It is not an understanding of atomic physics that is at issue here.

If those two assumptions are tossed, then all the fairy tale cosmological constructs fall away and well understood electrodynamic processes can adequately explain all the actual data we observe.

Ehm, no!

Food for thought: If there is a pervasive electrical field in space, analogous to the cosmic background radiation, could that explain the incredible energies we measure in cosmic rays?

Ehm, no! Read up on cosmic rays.

If there is an such an electric field of only a few micro-volts per meter, could such a field accelerate a charged particle to the energies we observe? We could never directly measure such a small electric field.

Read up on diffusive shock acceleration.

Space probe data indicates that the energy of the electrons of the solar wind INCREASES slightly as they get further away from the sun.

Reference please.

That means the existence of an accelerating force.

Nothing new.

There may be localized regions in space with vastly greater fields. Could these fields not accelerate electrons and other charged particles to high energies?

Indeed they do. Read up on diffusive shock acceleration and AGN jet physics.

If these high energy electrons then get deflected by the magnetic fields known to exist around stars and planets, would they not also emit plenty of synchrotron radiation

Synchrotron radiation is evidence of relativistic electrons and nothing else.

Re:Holy crap.

[Missing_dc]

wow, on behalf of the winners committee on /. (because of course none of us here are losers), I'd like to present you with this ribbon and a fucking cookie.

Enjoy, and thank you for you contribution to the conversation!!

close ?

[jacquesm]

This must be some meaning of 'close' that I was previously unaware of.

Re:close ?

[gpronger]

I was sitting in my office (Chicago) and the phone rang; two vendor reps wanted to drop by, being in the area, but needed some directions. As it happens they were in Peoria (central Illinois) which struck me as peculiar in saying that they were in the area. When they made it in, it turned out they were "in" from Australia. So in fact, from there perspective, they were "in the area".Seems things are all relative.

All things are relative, all relatives are things, my relatives took all my things.

Greg

Re:Holy crap.

[jacquesm]

'fucking cookies' are unpleasantly ambiguous.

Close to our Solar System

[Nethemas the Great]

We must have very different notions of close. I personally cannot begin to imagine how one could consider 190 million AU to be close.

Re:Close to our Solar System

[techno-vampire]

Compared to intergalactic space, 3,000 light years is practically next door. It's all relative, and when it comes to astronomy, anything inside the Milky Way is considered close.

Re:Close to our Solar System

[bradgoodman]

I believe the size of the universe would be 15 Billion light years - so 3000 is close.

If my calculations are correct - that would be like finding out that a random person from somewhere on earth - actually lived 27 feet away from you!

Re:Close to our Solar System

[eln]

Psh. You could travel that far in less than a year at Warp 9.9.

Re:Close to our Solar System

[xonar]

You could get there in 16.5 hours with a quantum slipstream drive.

Re:Close to our Solar System

[Spatial]

Sure. But if you go 0.1 faster than that, everyone turns into salamanders. Is it worth the risk?

Re:Close to our Solar System

[ChromaticDragon]

Interestingly enough, the universe is almost certainly much bigger than you believe.

Honestly, we have no idea and probably no real way of determining how big the universe really is. Nonetheless, the observable universe seems to be at least 90 billion light years in diameter. So, it'd be more like finding that random person in the same room.

Re:Close to our Solar System

[iris-n]

What? Wild leap of faith, my friend.

You are assuming that the universe is finite, and has been expanding at the speed of light from 15 billion years ago.

Actually, the big bang occurred about 13.73 billion years ago, and from that you can calculate the radius of the visible universe, which is about 13.8 billion light years.

The actual radius is unknown, as we don't know if the universe is finite or infinite, but it's at least 46 billion light years.

But yeah, it's pretty close.

Re:Close to our Solar System

[C18H27NO3]

The current estimation is believed to be ~13.7 billion light years with a diameter of ~93Gly, (46 billion light years in any direction out from Earth).((Comoving distance, cosmologicaql time, et al.)) 3,000 LY would equate to roughly 17,635,876,119,550,800 miles. 46G LY would equate to roughly 270,416,767,166,418,000,000,000 miles.

While not very close, it is a heck of a lot closer than if we were able to see it nearer the \edge\ of the observable portion of our universe.

Re:Close to our Solar System

[bradgoodman]

I was speaking very roughly - 15B ~= 13.9B. I am assuming the size of the universe is equal to the expansion from the big bang at the speed of light.

(I forgot about diameter vs. Radius though)

So revising my initial estimate - maybe more like 13ft.

Re:Close to our Solar System

[troll8901]

Huh?

No, no, the universe is merely a spheroid region, 705 meters in diameter.

Re:Close to our Solar System

[JLF65]

13.73 billion next Wednesday at 3:54 PM to be precise. ;)

Re:Close to our Solar System

[ceoyoyo]

The reason this gets called close is that these are high energy cosmic rays. The high energy ones get slowed down (lose energy) as they zip around the universe, so if we observe them they must originate fairly "close" to us. Close, that is, in comparison to the extra-galactic ones. 3000 light years is nothing, even on a galactic scale.

Re:Close to our Solar System

[K. S. Kyosuke]

"...that would be like finding out that a random person from somewhere on earth - actually lived 27 feet away from you!"

This happened to me - twice! - so I guess the astronomers might have indeed found a lump of dark matter. :-)

Re:Close to our Solar System

[aliquis]

How does that match with the big bang theory, 13.5-14 billion years old and nothing can travel faster than light? =P

I'm to tired to read it now, wherefrom come the estimated age? Not from the size and expanding at light speed or below I hope? Or well, if your number is correct that would still mean it's at least 45 billion years. So uhm, fail :D

I haven't read http://en.wikipedia.org/wiki/Age_of_the_universe yet :D

Re:Close to our Solar System

[aliquis]

Don't you mean the other way around? How could we tell big bang occurred 13.73 billion years ago? Much easier to see how far we can see I guess.

So shouldn't the longest distance to the far "edge" be 13.8 billion light years, which depending on where in space we are located mean that space have a diameter of 13.8 to 27.6 billion light years depending on if we are in the centrum or close to the edge (unless it's spherical and we can only see the "surface" where we are located and not the edge on the opposite side =P

Anyway, how can we go from that size to estimate how old it is? Because they expect it to expand at light speed?

Or do they get the age from it all being dark further away so it couldn't had started back then?

It gets fucked up in either way.

Or I've just lost myself, time for breakfast (and caffeine) :D

Re:Close to our Solar System

[aliquis]

Yes? As long as you don't go 0.1 faster. Quite obvious answer.

Ok, I put in the sound effect myself: "woosh", because I do understand it was like, a joke to get the salamander reference ;/

Re:Close to our Solar System

[Luyseyal]

How does that match with the big bang theory, 13.5-14 billion years old and nothing can travel faster than light? =P

Read about inflation.

-l

Re:Close to our Solar System

[Ambitwistor]

So shouldn't the longest distance to the far "edge" be 13.8 billion light years

No, because spacetime is curved and the expansion rate is neither constant nor equal to the speed of light.

The misconception is that the Big Bang was an explosion of matter into space, and there is some volume of space with matter in it and some volume outside of which no matter has yet reached.

In modern cosmology, the Big Bang is an expansion of space. There is no center or edge of the universe (although there is an edge of the universe we can see, because light hasn't yet reaches us from farther), and matter is distributed more or less uniformly everywhere in space. More details in this FAQ.

Anyway, how can we go from that size to estimate how old it is? Because they expect it to expand at light speed?

They look at the relationship between how far away objects are and how fast they're moving (via Doppler shift). This gives them the expansion history of the universe. Farther objects are older. Also, the structure of fluctuations in the cosmic microwave background radiation left over from the early universe depends on how the universe has expanded between then and now. When combined with the general relativity theory of cosmology and how the universe expands, you can back out an age estimate.

Re:Close to our Solar System

[Ambitwistor]

Space can expand at any rate, including faster than light. The FTL restriction is on matter/energy moving through space. It is not a restriction on the geometry of space itself.

As for where the estimated age comes from, your own link answers that.

Re:Close to our Solar System

[jagdish]

The universe is big. Really big. It may seem like a long way to the corner chemist, but compared to the universe, that's peanuts. (Douglas Adams)

Re:Close to our Solar System

[LEMONedIScream]

Also, from your logic, and assuming that everything comes from a single point, the universe would be 30 billion light years wide.

Light would expand outwards from the single point meaning that two rays of light on the same vector would travel away from each other at twice the speed of light...

Re:Close to our Solar System

[aliquis]

No shit.

Re:Close to our Solar System

[Mister_Stoopid]

I would say it is definitely worth the risk, considering it's impossible to go 0.1 faster.

the next logical question...

[fred fleenblat]

where is the dark antimatter?

Re:the next logical question...

[Anonymous Coward]

You're doing it wrong. Dark Matter is a bit of a misnomer.

Re:the next logical question...

[sleeponthemic]

I eated it

Re:the next logical question...

[Anonymous Coward]

I suppose it is in the same place that antimatter in general is. Very far away from normal matter.

Re:the next logical question...

[rrohbeck]

It seems that at least some dark matter particles are their own antiparticles since they can annihilate into gamma photons.

25%? Wait a minute..

[Anonymous Coward]

I thought it was supposed to be 75%?

I'm confused now.

Re:25%? Wait a minute..

[Anonymous Coward]

I believe you're thinking of dark energy - it's currently thought to be about 74% of the universe's mass/energy. Roughly 22% is guesstimated to be dark matter, and about 4% is "normal" matter.

Re:25%? Wait a minute..

[Anonymous Coward]

Dark ENERGY is about 75%.

And most popular dark matter theories propose that the dark matter particle is it's own antiparticle.

In Soviet Amerika

[Anonymous Coward]

Dark matter is the President!

Common doublespeak!

[east coast]

The universe is believed to be composed of about 25% dark matter, but there has been little evidence of it. This discovery, if correct, would be the first.

If this would be the first evidence how can we already have a little evidence of it?

Re:Common doublespeak!

[jd]

It would be more correct to say we lack evidence for viable alternatives, assuming the current models used, for which we now lack evidence unless evidence has been lacking on the existence of dark matter. Which may be great for grant checks, but it's lousy science.

Re:Common doublespeak!

[EveLibertine]

The things that are considered "evidence" of dark matter are things that match prediction models of things that would happen because of dark matter. Fancy stuff like high energy cosmic rays of certain types and the like. The trick is that there are also may be other models that predict similar types of events that are used as evidence of dark matter, but these models are models that exclude the possibility of dark matter

So, the evidence that points towards dark matter could also point towards other conflicting models of our universe, essentially being evidence for many different models at once. The reason discoveries of this kind of evidence is exciting is because it gives us something to look at and test so that we might select or eliminate from the groups of conflicting models.

Re:Common doublespeak!

[iris-n]

This is "news", not information.

What I find amusing is that the summary is an accurate resume of the article, which is thoroughly inaccurate.

The "little evidence" we have is the shape of colliding galaxies, of which the most famous is the Bullet Cluster, and gravitational lenses in regions that appear to be free from "normal" matter.

The exciting thing here is that they measured the actual energy spectrum of the beams, which could give insight on what are the particles of antimatter. That, AFAIK, we had no idea until now.

Re:Common doublespeak!

[Anonymous Coward]

Belief is not evidence. The belief is derived from theoretical models, i.e. it is a hypothesis. Evidence is based on observation. Both are part of the scientific method.

Of course if you are a christian then belief is evidence, and eventually you will end up with a conclusion that is logically equivalent to having monkeys fly out of your butt. But that would be for another topic....

Re:Common doublespeak!

[sleeponthemic]

There is a huge amount of numbers between zero and one. Duhh.

Re:Common doublespeak!

[Anonymous Coward]

They should have said "little direct evidence of it". We have plenty of evidence for it. Galaxy rotation curves (the speed at which the arms that galaxies move) require some form of extra mass to explain them, and the bullet cluster (google it for more info) is pretty solid proof that there is some form of non-baryonic matter out there. However, even though there is plenty of evidence for it, nobody has seen a signal directly from it (only the result of its effect on normal, baryonic matter). Finding direct evidence for DM would mean a trip to Stockholm.

Re:Common doublespeak!

[NeoSkink]

No other theory works as well as dark matter (as part of LCDM) to explain obersavations. Other theories have to be changed to account for what we observe at pretty much every scale. Those that work for Galaxy rotation don't work for clusters, which don't work for lensing, which don't work for early structure formation, and so on. Sure, one or two pieces of evidence may favor one theory or another over dark matter, but LCDM fits in the vast majority of cases, far more than any other theory.

Heck, you don't think that we scientists got together one day and said "I know, lets make up some goofy theory and then fudge the data to fit it!" do you? You do realize multiple theories were purposed, predictions were created, new data was taken, and conclusions drawn about which theories were supported by the new evidence, right? And that LCDM is the one that survived all the vetting? And that this process is still on going, yet LCDM still remains as the best theory?

Just checking... See, that's sort of how science is supposed (and in this case does) work.

Re:Common doublespeak!

[JLF65]

Heck, you don't think that we scientists got together one day and said "I know, lets make up some goofy theory and then fudge the data to fit it!" do you?

Actually, it's the other way around. Scientists looked at the data and saw it didn't fit, so they made up some goofy theories that "explained" why their calculations didn't match reality.

No! My theory isn't WRONG! It's ... err... invisible matter that can't be detected in any manner!! Yeah! That's the ticket!

Can you imagine if you did that in any other field??

Mathematician: And my theory shows conclusively that 2 + 2 is 5!

Person with firm grip on reality: Err... isn't 2 + 2 equal to 4? I can demonstrate with my fingers if you're having trouble visualizing it.

Mathematician: Actually, it IS 5, but the extra is carried away by invisible pixies that cannot be detected!

Re:Common doublespeak!

[Anonymous Coward]

Actually, it's the other way around. Scientists looked at the data and saw it didn't fit, so they made up some goofy theories that "explained" why their calculations didn't match reality.

OK, so scientists look at how galaxies behave and notice that they are behaving as if they had more mass than we can observe them having. Now there are two options: either 1. galaxies contain mass that hasn't been observed or 2. the theories of how the gravity works need to be revised. Both of these options are being studied, and so far the 'unobserved mass' hypothesis seems to explain obsrvations pretty well.

According to you, however, option 1 should have been discarded in the first place, for some ideological reason.

Re:Common doublespeak!

[aliquis]

Ohnoez, science goes the way of religion =P

Can we please keep the evidence as evidence and don't count theoretic results of theoretic theories as somewhat less trustworthy evidence? :D

Re:Common doublespeak!

[Ambitwistor]

Scientists looked at the data and saw it didn't fit, so they made up some goofy theories that "explained" why their calculations didn't match reality.

Yeah, uh, DUH. That's what science IS. You make up a theory to describe what you observe. If it doesn't fit, it's wrong, so you make up a new one and see if that works.

As another poster said, you seem to have some kind of ideological prejudice against the particular theory they came up with. But it's foolish to criticize them merely for coming up with a new theory in the first place. That's what they're SUPPOSED to do.

No! My theory isn't WRONG! It's ... err... invisible matter that can't be detected in any manner!! Yeah! That's the ticket!

So you're mocking the idea that there can be particles out there which don't interact with light, despite the fact that we know such particles exist, e.g., neutrinos? The main difference between neutrinos and dark matter is that dark matter needs to be heavier than neutrinos. And dark matter particles have been PREDICTED to exist for entirely independent reasons in order to explain other mysteries in particle physics; indeed, the Standard Model itself arguably already contains dark matter candidates (axions). According to you, this is an insane idea to be derided, despite the fact that its predictions agree with numerous observed phenomena including galactic rotation curves, galactic cluster orbits, large-scale structure formulation, cosmology and the CMBR, gravitational lensing, galaxy collisions, etc.

Re:Common doublespeak!

[niklask]

Heck, you don't think that we scientists got together one day and said "I know, lets make up some goofy theory and then fudge the data to fit it!" do you?

Actually, it's the other way around. Scientists looked at the data and saw it didn't fit, so they made up some goofy theories that "explained" why their calculations didn't match reality.

You have no idea how the scientific model works, do you? With your reasoning we should never have adopted relativity as the theory describing gravitational interaction and instead stuck with newtonial mechanics, even though more accurate observations of planetary orbits etc showed that newtonian mechanics wasn't correct.

No! My theory isn't WRONG! It's ... err... invisible matter that can't be detected in any manner!! Yeah! That's the ticket!

Again, no clue how the scientific model works. BOTH options have been scrutinized. Problems is that relativity works SO WELL in other cases and if we modified it, which could lead to potential problems in those cases where it really works. Occam's razor applies here.

Add to this the strong hints from particle physics that there should be more particles out there.

Can you imagine if you did that in any other field??

Mathematician: And my theory shows conclusively that 2 + 2 is 5!

Person with firm grip on reality: Err... isn't 2 + 2 equal to 4? I can demonstrate with my fingers if you're having trouble visualizing it.

Mathematician: Actually, it IS 5, but the extra is carried away by invisible pixies that cannot be detected!

Bad, bad example. First of, you cannot compare mathematics with physics. Secondly, you can easily construct a mathematically theory in which 2+1=0 and not 3 (this is part of group and ring theory in mathematics). Just because you intuitively are familiar with one theory does not make the other one incorrect. It may not apply to the same problem, but that does not make it incorrect. In physics however, you have a data set, and your model is supposed to describe this. Its very different.

Btw, do you now the history behind the neutrino? It was proposed because the energy spectrum of the electron produced in beta decay was continuous, which it wouldn't be if it was a two-body problem. So it was proposed that there was a third particle involved, the neutrino, that we could not detect but which carried away part of the energy in the decay. Much later, we actually detected neutrinos, and now we detect them on a daily basis. With this hindsight, why is it so implausible that there are neutralinos (the lightest of the supersymmetric particles) out there or some other for of dark matter which we cannot detect with the technology of today?

To me, it seems you are just a skeptic because you do not have a clue about the theories involved.

Re:Common doublespeak!

[Ambitwistor]

Now there are valid hypotheses rooted in conventional physics that explain galaxy motion and other astronomical observations and don't depend on dark energy/dark matter

Name one that agrees with all the observations as well as dark matter does. And I mean ALL the observations, not just one particular set of observations that the theory happens to do well on. Science has to be consistent with all available evidence, not just the evidence you cherry pick.

Re:Common doublespeak!

[Ambitwistor]

Sheesh. Grow a clue.

"The theory passes numerous observational tests" != "ZOMG science is religion!!1!!".

Re:Common doublespeak!

[niklask]

Well actually that is what astronomers did, and it's profoundly absurd.

It is not, and this just shows your ignorance. You should read up on the history of the neutrino. Or read up on the history of atom.

Can you imagine doing that in another scientific discipline?

Biologist: Well I can't account for the development of this organism so I'll just invent another "invisible" type of genetic coding mechanism that no one has ever detected before to explain it!

Again I remind you of the neutrino. Are you saying that neutrinos do not exist?

I'll call it INA (Invisible Nucleic Acid)!

Layperson applying simple logic: Why would you do that? Why not just try and look at all the conventional theories and explicate the organism's development in the confines of those theories and known genetic knowledge instead of creating a new "invisible" NA (nucleic acid) that no one has ever seen or heard of before?

Geneticist: Because that's not interesting enough and it won't get me published frequently enough!

Layperson: Of course

Now here's the situation with Astronomers, they find that galaxies behave in ways they didn't expect, and in ways that look like they have more mass than they should have.

They (we) ARE using conventional physics, i.e. relativity theory and that does not work. Modifying relativity or even newtonian mechanics does not work very well.

If you think this is all about publishability, then you are painstakingly mistaken and should freshen up your physics 1-2-3.

So going by simple logic should they:

A. Make up a new form of matter that has never been observed in the history of science to explain such observations?

Because that has never happened before, right? Physics has not improved with technology. We really do not detect protons and neutrons and electrons, and quarks are just a figment of our imagination. Again, read a little about neutrinos. Just because we cannot detect something does not mean its not there. Thinking so, just shows ignorance.

or

B. Exhaust every conventional explanation first which is limited to known physics principles and known types of matter?

Has been done already. Claiming its either or, just shows how little you know about the field.

Well if you want to do honest science you choose B,

That is so not honest science. Honest science does not discredit any option like you just did.

but if you want to carve out a niche for yourself and get published more frequently even if you're doing bad science and you end up wasting decades of valuable scientific research time on a shaky hypothesis that would get any normal person laughed out of a observatory, you choose A.

Sigh.

Now there are valid hypotheses rooted in conventional physics that explain galaxy motion and other astronomical observations and don't depend on dark energy/dark matter/unicorns/leprechauns, but the astronomical community needs to have the intellectual honesty to examine them closely and thoroughly before they even think of creating alternative types of matter or energy.

They are dismissed because they are not viable theories. They have been examined and scrutinezed and found to be not complete or not working. MOND (modified newtonian dynamics) requires an arbitrary change in the interaction. There is no explanation why, it is just there because it makes things fit nicely. And the results from MOND are not unambiguous. For some galaxies you would have to change the interaction in a slightly different way than other galaxies, to match the rotation curve. Where as with dark matter you get an incredible match with the SAME physics for ALL galaxies. Now which one is more plausible?

Re:Common doublespeak!

[niklask]

This is "news", not information.

What I find amusing is that the summary is an accurate resume of the article, which is thoroughly inaccurate.

Your post is not accurate either.

The "little evidence" we have is the shape of colliding galaxies,

Its interacting clusters of galaxies, not colliding galaxies. And its more than the shape. Its the difference in where weak lensing show concentrations of matter and where X-ray observations show where hot intergalactic gas is.

of which the most famous is the Bullet Cluster, and gravitational lenses in regions that appear to be free from "normal" matter.

Sometimes the weak lensing maps show lensing where there are very little ordinary luminous matter, but this far from the only case. There are weak lensing maps showing stronger lensing than would be expected from just the luminous matter.

The exciting thing here is that they measured the actual energy spectrum of the beams, which could give insight on what are the particles of antimatter. That, AFAIK, we had no idea until now.

You are very wrong. What they observe is electrons and positrons, neither of which is a new discovery and neither is unknown. The insight that can be gained is how these were produced.

Re:Common doublespeak!

[iris-n]

The only inaccurate thing about my post is the last bit, about antimatter. It's a typo. Substitute antimatter with dark matter and the sentence makes sense. I told that the energy spectrum of the electron beams can lead to insight on how they were produced, i.e. the mass of the dark matter particles. And they haven't observed positrons, they're just predicted by some theories, in this case the Kaluza-Klein model.

Its interacting clusters of galaxies, not colliding galaxies. And its more than the shape. Its the difference in where weak lensing show concentrations of matter and where X-ray observations show where hot intergalactic gas is.

I concede, it would be more accurate to say clusters of galaxies instead of galaxies, with a negligible loss of communicating power.

But no. They are colliding. You can have numerous types of non-destructive interactions between clusters, none of which is shoving a cluster trough another. If you don't want to call that a collision, I think you'd be very lonely in the astrophysics community.

And the x-ray observations are used to determine the distribution of baryonic matter, and thus calculate were the centre of mass should be. The gravitational lensing shows were the actual centre of mass is, and they are not the same.
That is, we have a difference between the actual shape and the one we would have expected from the baryonic matter we see. Now, if it is too much a leap for you associating the centre of mass of a cluster with its shape, I'm sorry. I should have been clearer.

Frankly, it's all in the wikipedia I've linked. So that the interested parties could gather information on how the calculations were made. If I had talked straight about the methods as you did, I doubt many would have understood. My point is not to show off knowledge (I'm very secure of that, thank you), is to distribute some.

Slashdot is a great forum to discuss technical matters, but when it comes to actual science, the general level of knowledge is very low.

Re:Common doublespeak!

[Goaway]

We don't have "a little" evidence, we have "little" evidence. These are two distinct concepts in English. Just "little" is usually understood to contain "no" as possible value.

Re:Common doublespeak!

[phosphorylate this]

No idea about the dark matter question, not my field. However we should always welcome the (respectful) questioning of fundamentals in science.

Heck, you don't think that we scientists got together one day and said "I know, lets make up some goofy theory and then fudge the data to fit it!" do you?

I'm a scientist and see, or catch myself doing, this quite often for the small-questions I am normally involved in working on. Thus I can easily imagine collective-blindness allowing it to occur for the BIG-questions too.

The "fudging" is usually not deliberate of course. It is not like I sit there making up numbers to massage a key graph just because I had a goofy idea and am seeking fame (wrong field for fortune). Instead I would say my "fudging" occours at insideous and difficult to detect stages that are basically the scientific equivalent of sloppy-workmanship:

1) Shaky foundations
Assuming a fundamental idea which my work builds upon is proven only to later realise alternative explanations exist for the data from which the fundamental idea was derived. Ideas become more familiar and acceptable with repetition, yet they do not become more scientifically sound without better experiments. This is an easy trap to fall for and I have done so on several occasions.

2) Artifact hunting
Selective reporting of "sucessful" experiments based upon a faulty theory. If I propose a theory there are always multiple ways of testing it, each with their own set of controls that I can concieve of. I normally proceed by setting up trial experiments to get an idea for the size of my signal in each case and the background and artifacts of each tecnique. If you fail to concieve of the correct control for one technique it is easy to spend a month or two measuring an artifact.

For example in the current paper I would not be suprised if they searched the sky for cosmic rays with the expected energy spectrum before checking background emmissions at other energies. While you are of course hunting for the signature of dark-matter you are also hunting for artifacts in the right energy-range. Without getting out into the universe it may be some time before we understand all possible mechanisms of cosmic ray production.

3) Alternative explanation blindness.
If can be quite difficult to understand all the possible artifacts in any experiment let alone account for them and seek to eliminate their influence.

For eample, the constant reporting of geological evidence for past-water on Mars presupposes that we fully understand martian geology. It took us a lot of effort and measurements to understand mineral formation on earth to the level we do now. There will of course be many parallels between the two planets geological histories. But to me at least the idea that we can understand all possible mechanisms of mineral formation in an atmosphere and planet we have not visited seems a tad hasty.

Eventually science will eliminate hasty ideas and catch incomplete experiments. But don't underestimate the ease with which these ideas spread in science or the amount of effort it takes to catch them.

Re:Common doublespeak!

[niklask]

The only inaccurate thing about my post is the last bit, about antimatter. It's a typo. Substitute antimatter with dark matter and the sentence makes sense. I told that the energy spectrum of the electron beams can lead to insight on how they were produced, i.e. the mass of the dark matter particles. And they haven't observed positrons, they're just predicted by some theories, in this case the Kaluza-Klein model.

Yes, I jumped the gun a little too fast. My mistake.

Its interacting clusters of galaxies, not colliding galaxies. And its more than the shape. Its the difference in where weak lensing show concentrations of matter and where X-ray observations show where hot intergalactic gas is.

I concede, it would be more accurate to say clusters of galaxies instead of galaxies, with a negligible loss of communicating power.

But no. They are colliding. You can have numerous types of non-destructive interactions between clusters, none of which is shoving a cluster trough another. If you don't want to call that a collision, I think you'd be very lonely in the astrophysics community.

That is why I used the term interaction, and that is the term most of my co-workers (also astrophysicists and cosmologists) use.

And the x-ray observations are used to determine the distribution of baryonic matter, and thus calculate were the centre of mass should be. The gravitational lensing shows were the actual centre of mass is, and they are not the same. That is, we have a difference between the actual shape and the one we would have expected from the baryonic matter we see. Now, if it is too much a leap for you associating the centre of mass of a cluster with its shape, I'm sorry. I should have been clearer.

Frankly, it's all in the wikipedia I've linked. So that the interested parties could gather information on how the calculations were made. If I had talked straight about the methods as you did, I doubt many would have understood.

If you by "shape" mean "shape of the mass distribution", then yes I fully agree. But shape is more general in that, and since you were talking about galaxies, it sounded like you were talking about the shape of the galaxies.

Now I understand what you actually meant and I think we could have very meaningful discussions.

My point is not to show off knowledge (I'm very secure of that, thank you), is to distribute some.

Add my point was to add to that information distribution, not to "show off". You are not the only secure one.

Slashdot is a great forum to discuss technical matters, but when it comes to actual science, the general level of knowledge is very low.

On this point I very much agree. The problem with Slashdot is, as I see it, that it is a written forum and because of that it is not the same as a verbal one. In a verbal conversation I would probably have asked "what do you mean by shape?" and the conversation would have progressed from that.

Re:Common doublespeak!

[budgenator]

Scientific theories about thing in normal world scales tend to be pretty comfortable psychologically, move into cosmological or quantum scales and things can get goofy real quick, I suspect that truly understanding Quantum Mechanics is a sign of psychosis.

Re:Holy crap.

[spazdor]

Over there, next to your regular one.

Bad summary.

[JohnnyDanger]

The summary misinterprets the results.

The instrument detects high-energy electrons. They found an excess (only 70, but statistically significant) with a particular energy, which if they come from a galactic source (like a pulsar), that source must be within 3000 light years. However, the researchers can't find an appropriate source.

Alternatively, this could be due to annihilating dark matter---the energy spectrum matches some models---but that's not necessarily coming from a particular source.

Re:Bad summary.

[siride]

They aren't selling anything. They are just coming up with ideas to explain things many light years away (i.e., not particularly relevant to business practices).

Re:Bad summary.

[Zwicky]

They are just coming up with ideas to explain things many light years away (i.e., not particularly relevant to business practices).

Are you not familiar with the term 'vaporware' ;)

Re:Bad summary.

[Anonymous Coward]

And yet there are two pulsars within 300 pc of the solar system: Geminga and Vela. This is very similar to the previous PAMELA result with positrons and each could be explained by either of these two sources.

Re:Bad summary.

[budgenator]

Astronomers are probably the oldest priesthood, and many astronomers financed their observations by casting horoscopes. A couple millennium ago correctly predicting a lunar or solar eclipse would make you a demigod in the eyes of the common man.

Kinda Reminds Me of the Face on Mars

[Louis Savain]

If you believe that extraterrestrials once lived on Mars and elsewhere in the solar system, then every little hill will look like an intelligently designed artifact. If you believe in dark matter, then every little unexplained phenomenon becomes evidence for dark matter. It's mostly a matter of faith. The same goes for all the other weird inventions of cosmology. I see very little science in this sort of things.

Heck, we have no clue, really, as to what make things fall or even why bodies move, and yet some feel they know enough to come up with all sorts of half-baked conjectures based on their incorrect and incomplete understanding. Unless and until physicists can fully explain the true mechanism of movement in language that the layperson can understand, I'll remain highly skeptical of their more outlandish conclusions (black holes, wormholes, dark matter, dark energy, big bang, parallel universes, etc.), sorry.

Re:Kinda Reminds Me of the Face on Mars

[s.bots]

Unless and until physicists can fully explain the true mechanism of movement in language that the layperson can understand, I'll remain highly skeptical of their more outlandish conclusions (black holes, wormholes, dark matter, dark energy, big bang, parallel universes, etc.), sorry.

How do you expect the explanations in layman's terms to be any different than what we use now (what goes up must come down, at equilibrium every action has an equal and opposite reaction, object at rest stays at rest until acted upon, etc. etc. etc.)? These are extremely complex phenomena that, if described in layman's terms, cannot be accurately portrayed.

Re:Kinda Reminds Me of the Face on Mars

[purpleraison]

I bet you believe in creationism too, huh?

I understand the argument you're making, it's the old 'if it's a horse, it's a horse; not a zebra' argument. However, physicists are not willy-nilly declaring stuff dark matter because that's what they want to find. There is actually a lot of hard-core science to support what you call

outlandish conclusions(black holes, wormholes, dark matter, dark energy, big bang, parallel universes, etc.)

The fact that YOU don't understand it is more a statement about yourself, not the science.

Re:Kinda Reminds Me of the Face on Mars

[Louis Savain]

The fact that YOU don't understand it is more a statement about yourself, not the science.

Pot calling kettle black. Show me one human being who truly understands the mechanism of movement. Dark matter and dark energy are inventions that physicists conjured up in order to hide the fact that their current theory of gravity (GR) is falsified. That's all. When they truly understand gravity and movement, then they'll have a leg to stand on. In the meantime, it's no better than creationism.

Re:Kinda Reminds Me of the Face on Mars

[sleeponthemic]

These are extremely complex phenomena that, if described in layman's terms, cannot be accurately portrayed.

Unless you had an Etch A Sketch handy. In which case, so accurate, you have created a new, carbon copy universe on the screen.

Re:Kinda Reminds Me of the Face on Mars

[Cadallin]

And what precisely is the observation or experiment that falsifies General Relativity?

Re:Kinda Reminds Me of the Face on Mars

[morgan_greywolf]

Not that I'm trying to defend the parent poster (because I disagree with him), but while I'll say that GR is not truly falsified, but it is probably incomplete. The biggest problems are quantum gravity and spacetime singularities. See this discussion, which includes details about Hawking radiation, black holes, dark matter and so forth.

Re:Kinda Reminds Me of the Face on Mars

[Zorque]

Are you for real? I can't see or feel carbon dioxide, it must be a myth! Things don't wait for our technology to catch up to them before they start existing, just because we couldn't see bacteria until we invented microscopes doesn't mean they didn't exist before then.

Re:Kinda Reminds Me of the Face on Mars

[Ambitwistor]

Savain isn't a creationist, but he is a well-known physics crackpot. He's been promoting his B.S. for over a decade; just search the 1990s archives of the Usenet sci.physics.* groups. He emotionally can't accept the mathematical notion of spacetime, because he claims that "nothing can move in spacetime", which only proves that he misunderstands the whole concept. (Thus his claim above that physicists have been unable to explain the concept of "movement".) He usually then proceeds with long, profane rants against various respected physicists. You know you're on the receiving end of a classic Savain rant when he starts raving about "chickenshit voodoo physicists".

Re:Kinda Reminds Me of the Face on Mars

[Anonymous Coward]

I believe every time something intellectual is posted on the internet, some moron will chime in thinking he knows more than the experts and talk how smart they are and how wrong everyone else must be.

Maybe that belief is why your post seems to fucking moronic.

Or maybe its just that it is.

Re:Kinda Reminds Me of the Face on Mars

[invisiblerhino]

That's all. When they truly understand gravity and movement, then they'll have a leg to stand on. In the meantime, it's no better than creationism.

Whoa there!

Let's be crystal clear on this. There is plenty of evidence for various aspects of GR. If you really want, you can mess around with Modified Newtonian Dynamics, but, to quote the wiki article on GR, it's 'the simplest theory that is consistent with experimental data'.

What do you mean 'truly understand gravity and movement'? If you mean predict how objects will move under gravity with unparalleled precision, then I think we're already there. I'm not sure what else science could tell you. I'm not a big dark matter/energy fan either, but if all observations agree with their existence, so do I.

Re:Kinda Reminds Me of the Face on Mars

[budgenator]

In a universe where as many as 18 dimensions may exist and neutrino oscillate in flavor as the move, I'll bet there are still some deep questions about movement and gravity that'll earn some team a Nobel or two.

Re:Kinda Reminds Me of the Face on Mars

[Cadallin]

You're disagreeing with the wrong person then. I'll readily acknowledge that General Relativity and the Standard Model are incomplete. I'll even guess that they may be outright wrong in some places.

But (!), that's not what the poster I originally replying to was saying. He was claiming that because we don't know everything, that we know nothing. Completely false. We may not know everything, but we can place some pretty tight tolerances on what the predictions of a complete (or just more complete) theory must say about the world under an awful lot of conditions.

Re:Kinda Reminds Me of the Face on Mars

[Cadallin]

and to elaborate on what I was saying (because I hit submit and then immediately realized I should have specified how what I said related to what the post you replied to was saying):

General Relativity and the Standard model are too accurate in too many places. We know that a better theory to replace them nearly has to predict almost the exactly the same things that they do. Any more complete theory has to predict (or otherwise explain why experiments to test for these phenomena appear to be positive) in a VERY rigorous way all kinds of phenomena. And that includes "weird stuff" like the things that clearly make the GGP in the thread doubt physic's understanding. Thing's like:

1. The phenomena of Wave/Particle Duality.

2. Constant Speed of Light for all observers.

3. Time Dilation

None of these things, and a host of other "weird stuff" that makes ignorant lay people think modern physics is full of shit are going anywhere.

Great stuff

[DanoTime]

This is really interesting, I'd never even heard of the studies they were performing until now and I found the link - as spock would say... fascinating. (raise eyebrow at the appropriate time) What a boon for LSU physics department! I guess the school isn't so Mickey Mouse after all... http://www.lsu.edu/

Re:Great stuff

[Ambitwistor]

LSU physics doesn't suck. They have 8 faculty working on aspects of general relativity, whereas most departments don't even have one — due partly to their proximity to the LIGO gravitational wave observatory.

FTL Particles

[xonar]

Do these particles travel faster than light? Could it be used as a form of communication? IS it used as a form of communication?

Re:FTL Particles

[Tenebrousedge]

No, no, and the last question is probably a no, but you could elaborate on what "it" refers to for a more definite answer.

Information cannot propagate faster than the speed of light. The speed of light is an absolute limit.

Re:FTL Particles

[xonar]

What about theoretical particles like tachyons? I was not sure if the article referred to anti-electrons commonly associated w/ anti-matter collisions (or is that a matter-antimatter collision). I am also not familiar with the basic nature of said particles, as I have only a casual interest in such physics. I was also stoned when I wrote that, the thought of aliens using a galactic standard FTL data transmission technique (unbeknownst to humanity, yet), peaqued my interest.

Re:FTL Particles

[Tenebrousedge]

Being stoned is pretty good.

The short answer is that that tachyons can't transmit information. The short explanation is that Einstein's theories prevent it.

Anything with mass cannot reach the speed of light; it would require an infinite amount of energy. Anything without mass travels at the speed of light. Tachyons are obtained by throwing imaginary numbers into the mix.

Dark matter is thought to be matter that does not interact with other matter except gravitationally. We don't have much of an idea what that would look like, but it would obey the rest of the physical laws as we understand them.

If you have any other questions I can try to answer them. Wikipedia has a good article on faster-than-light.

Also, I hope that you don't mind me correcting you, but the the word is 'piqued'.

Re:FTL Particles

[xonar]

Dark matter is thought to be matter that does not interact with other matter except gravitationally.

"In physics, the fifth dimension is a hypothetical extra dimension beyond the usual three spatial and one time dimensions; e.g. physicists have speculated that the graviton, a particle thought to carry the force of gravity, may "leak" into the fifth or higher dimensions which would explain how gravity is significantly weaker than the other three fundamental forces." (Wikipedia)

Kaluza-Klein Theory

Site that attempts to visualize higher dimensions (java required)

I don't really know where I'm going with this, but it makes for interesting reading.

Grammar correction accepted.

Re:FTL Particles

[xonar]

The speed of light is an absolute limit.

Could this barrier be theoretically broken with use of a higher dimension?

Subspace Communication (Excuse the reference :P)

Re:FTL Particles

[budgenator]

The assumption would be that tachyons travel faster than the speed of light and lose energy by going fasater so they would need infinite energy to decelerate to slower than the speed of light. The real problem is crossing the barrier with mass; not being on one side or the other. If tachyonic matter really existed it's interactions should produce photons which would be visible to us. and we haven't seemed to have seen any so far.

Re:FTL Particles

[Anonymous Coward]

Not really. The speed of light should been seen not as the speed that light happens to travel at, but a fundamental universal constant.

From wikipedia:

Special relativity reveals that c is not just the velocity of a certain phenomenon, namely the propagation of electromagnetic radiation (light)--but rather a fundamental feature of the way space and time are unified as spacetime. A consequence of this is that it is impossible for any particle that has mass to be accelerated to the speed of light.

Re:We''ll likely see more research like this.

[Anonymous Coward]

With Obama in charge, ALL matters will be dark matters!

LHC

[theonewho]

hi,

a ~650 GeV parent would, in a final state including leptons,
possibly be in reach of ATLAS and CMS at LHC if it can be
produced in high-energy quark and/or gluon interactions

cheers,
kevin

Are you kidding ?

[Anonymous Coward]

How is 3000 light years away CLOSE to our solar system ??

Friggin' Alpha Centauri is only 4.4 light years away, and thats not really CLOSE by any stretch of the imagination.

Our entire galaxy is 100,000 light years across and we are 26,000 light years from the galactic center, so ACTUALLY this dark matter is about 1/8 of the distance between us and the CENTER OF THE GALAXY .... YEAH, real close, brainiac!

There is no such thing

[American Scum]

I still believe that 'dark matter' is only a temporary constant inserted into an equation modern scientists don't truly understand.

In time they will discover what is causing the effects of this 'dark matter' - it will not be super strange matter, nor another form of matter, but will be either a change in the overall calculations of our universe's energy or it will be some type of substance that was not accounted for.

Theorists throw in some offbeat number to the calculation every 30 years or so to account for what they just can't figure out.

Re:There is no such thing

[rrohbeck]

Well *something* is warping spacetime this way and that, and that's what they call dark matter and dark energy respectively. Now the question is what does the warping.

Re:There is no such thing

[S3D]

You probably mistake dark energy for dark matter. Dark energy is indeed most probably a cosmological constant and related to the energy of universe. Dark matter is completely different thing - it's an invisible mass causing anomalous speed distribution of the galaxies in the clusters, stars in the galaxies and most spectacular - shape of the Bullet Cluster

Re:There is no such thing

[Ambitwistor]

In time they will discover what is causing the effects of this 'dark matter' - it will not be super strange matter, nor another form of matter, but will be either a change in the overall calculations of our universe's energy

"Calculations of our universe's energy" don't have anything to do with the fact that gravitational orbits don't look right. There are basically only two posibilities: there is an unseen source of gravity, or gravity doesn't work the way we think. Both options have been explored, and the first agrees best with all the data.

or it will be some type of substance that was not accounted for.

You mean some unknown substance which we haven't been able to see, but which affects orbits ... like, I don't know, "dark matter"?

There are already strong constraints on what kind of substance dark matter can be. It's not large dark objects like brown dwarves and black holes; those would have been seen in microlensing surveys. (Indeed, some were seen, but not nearly enough to account for the observed gravitational effects.) It's not ordinary baryonic matter (made of protons and neutrons) at all; that would have completely altered the ratio of elements created in the Big Bang to something we don't observe. It's not light particles like neutrinos; "hot dark matter" doesn't consistently explain all the observations like how galactic and supercluster structure was seeded in the early universe. For these and many other reasons, the evidence points toward it being a massive weakly interacting particle. Such particles have already been theorized to exist in particle physics for other reasons, e.g., to solve the strong-CP problem in the Standard Model or to explain the hierarchy problem or grand unification. Indeed, it's somewhat hard to write down a theory beyond the Standard Model that doesn't naturally include a dark matter candidate.

Re:There is no such thing

[Man Eating Duck]

It's not ordinary baryonic matter (made of protons and neutrons) at all; that would have completely altered the ratio of elements created in the Big Bang to something we don't observe.

Thanks, your post answered several of my questions.
If you have the time, could you explain a bit more about this ratio? What implications would it have if dark matter consisted of baryonic matter? Honest question, I simply don't know :)

Re:There is no such thing

[Ambitwistor]

This is how I recall it: if dark matter was baryonic, then the early universe would have produced a lot more helium and less deuterium. Deuterium has 1 proton and 2 neutrons; helium has 2 protons and 2 neutrons. If there are a lot of extra baryons (protons and neutrons) around, it's easy for them to collide with existing deuterium atoms and produce helium. I think ...

Also, if there are a lot of baryons around, I think the early universe doesn't "clump" enough to produce the superclusters and things we see today. I think this is because the dark matter doesn't interact electromagnetically and so is able to start clumping earlier. The cosmic background radiation is an independent check, because the non-baryonic "clumping" is also visible in fluctuations in the CMBR where denser matter affected the local radiation — non-baryonic clumps could already exist and grow by the time the CMBR was formed (~400,000 years after the Big Bang).

Don't take everything I say as 100% correct; I can't remember all the details of how this works.

Re:There is no such thing

[Man Eating Duck]

That clears it up a bit - thanks!

link to full article

[vindimy]

Here's another link to full article. It's quite scientific, not for your average slashdot reader.. :/

Big whoopie

[Konster]

Big deal. I find dark matter every time I turn out the lights.

This is science?

I believe I speak for us all...

[Anonymous Coward]

pics or it didn't happen.

I have some dark matter under my bed

[Flentil]

I have some dark matter under my bed. I don't really know what it is without shining a light under there. I only know it's there because when I try to cram in more stuff, it bumps into the dark matter. Silly isn't it? What's more silly is that this is exactly how astronomers classify dark matter. Something they think is there but aren't sure because they can't see it.

Dark matter is not magic. It could be an asteroid belt of non-glowing rocks. That would totally count according to the definition, and is actually one of the more likely explanations of what 'dark matter' really is. It's not all that mysterious. And anyway, it's all based on some mathematical calculation of how much mass they think is floating around in space. If the math is wrong, the whole thing could be a complete fantasy. So no big deal, really.

Re:I have some dark matter under my bed

[Anonymous Coward]

Are you retarded? It's not called "dark" matter because it's dark in color. It's a theoretical particle that is largely assumed to exist because it explains several things that otherwise would go unaccounted for in our current physics model. But I'm sure your independent armchair research beats that of some of the world's top minds, and people who have been doing this for years and know what they're talking about.

Re:I have some dark matter under my bed

[Ambitwistor]

It could be an asteroid belt of non-glowing rocks. That would totally count according to the definition, and is actually one of the more likely explanations of what 'dark matter' really is.

No, it isn't. It's not baryonic at all (made of protons and neutrons); if it was, that would have produced ratios of elements in the Big Bang which disagree with the ratios we observe.

And anyway, it's all based on some mathematical calculation of how much mass they think is floating around in space. If the math is wrong, the whole thing could be a complete fantasy.

We have a good idea of how much mass is floating around in stars, and in gas, and in dust, and now even in dark bodies like brown dwarfs. The estimate could be off, but it's not off by the factor of 10 necessary to get rid of the need for dark matter. And it's not just the amount of matter, it's the distribution of matter that matters. In order to get the observed galactic rotation curves, matter has to be distributed in a particular way. If there's more mass out there, but it's distributed in the same way as what we see, it doesn't work. Either way, there "missing mass" which is out there unaccounted for.

What's dark matter anyway?

[Anonymous Coward]

So what's the difference between dark matter, normal matter, and antimatter? Is dark matter just normal matter that's really...dark? Then it would absorb all visible light but it would have to emit infrared wouldn't it?

Re:What's dark matter anyway?

[budgenator]

just assume that dark mater exists in a way that is only able to interact with matter and antimatter through gravity and you'll be close enough for a layman.

I worked with Dr. Guzik and Dr. Wefel

[Anonymous Coward]

I thought some of you Slashdotters would find it interesting that I actually worked very closely with Dr. Guzik and Dr. Wefel on a related experiment last year at LSU. I had the privilege of talking with them quite a bit about their ATIC experiment and I must say, they are one talented group of scientists. Looks like I'll need to get my hands on a copy of this paper!

Correction

[AlanS2002]

The universe is believed to be composed of about 25% dark matter, but there has been little evidence of it. This discovery, if correct, would be the first.

No it would be evidence of "a large amount of high energy cosmic rays".

I know where all the dark matter is

[DreadPiratePizz]

It's in my massive muscular physique!

Pfft, theres closer than that!

[Anonymous Coward]

I had some dark matter in the toilet earlier today

Well, it is relative

[someone1234]

Considering there are gazillions of galaxies, and each of them are farther than our own galaxy's center, it is damn close.

Think of it this way: 3000 lightyears means, if that dark matter comes this direction maximum speed (at the speed of light), we have only 3000 years to try and avoid it.

3000 light years???

[advocate_one]

meh... come back and wake me up when it gets to 300 light years...

on a secondary note, I wonder if the solar system has passed through several "clouds" of this stuff during its lifetime? Could explain major die-offs on Earth...

Re:3000 light years???

[Anonymous Coward]

on a secondary note, I wonder if the solar system has passed through several "clouds" of this stuff during its lifetime? Could explain major die-offs on Earth...

Based on what?

-1 physics

[drerwk]

You link to Technetium-99m which is an excited nucleus that undergoes gamma decay. And you claim that there are no moving charges by which this gamma ray is generated. I link to A Brief Review of Nuclear Physics http://galileo.phys.virginia.edu/classes/252/Nuclear_Notes/nuclear_notes.html and quote the section on gamma decay

gamma-decay The gamma rays are just high-energy photons, of order 100 keV to a few MeV. Emission of gamma rays is similar (but at much higher energies) to emission of photons by excited states of atoms. The nucleus can be excited by having just emitted an alpha or beta, or by colliding with another nucleus, or being bombarded by neutrons, say. All these events can lead to a nucleus in which the charge distribution is oscillating, and electromagnetic radiation ensues.

Same idea for the positron - electron collision - those are clearly not at rest.
If you choose to correct Prof. Fowler on his understanding of nuclear physics I hope you will post the dialog here; /. is not as funny as it once was and I miss those days.

Re:-1 physics

[ceoyoyo]

The positron-electron releases far more energy than the sum of the kinetic energies of the particles unless you get them going REALLY fast. Most of the energy comes from non moving-charge processes.

Also note that neutrons and anti-neutrons annihilate. Neither is charged. Yes, they're both composed of charged quarks, but the energy released is far more than the kinetic energy of any of the constituent particles.

It's not particularly insightful to claim that you can't create EM radiation without charged particles since we don't know of any uncharged fundamental matter particles (yet).

Re:-1 physics

[niklask]

Same idea for the positron - electron collision - those are clearly not at rest.

Plain wrong. Talk to any particle physicist worth his/her name. The photons created in electron-positron annihilation is not due to moving charges.

Re:-1 physics

[arminw]

....All these events can lead to a nucleus in which the charge distribution is oscillating, and electromagnetic radiation ensues.....

So when a charge oscillates it doesn't experience acceleration? Anytime a charge carrier, be it electron, positron, muon, proton, or whatever, is accelerated, photons can be generated. That is an EXPERIMENTAL observation right here on earth. Whether that acceleration happens in the nucleus of an atom or elsewhere makes no difference. When the electrons in a conductor oscillate, ie. are accelerated back and forth by an alternating electric field, that conductor radiates photons, the energy of which depend on the rate (frequency) of the oscillation. In every day life, we call such a conductor an antenna.

Not only that, but photons can also knock electrons out of their atomic orbits. This is called the photoelectric effect. It is reversible. It is at the basis of all modern photon sensing devices, such as electronic cameras etc. Such loose electrons will in turn interact with an electric or magnetic field. If there is an electric field, it will accelerate the electron. That electron can then hit other atoms and knock more electrons free. These in turn can be further accelerated an repeat this avalanche process. Photomultiplier devices use the photoelectric effect in both directions for extremely sensitive photon detectors.

I think you don't quite understand Prof. Fowler. Accelerated charges is the ONLY way to produce photons. Whether these charges are within atomic nuclei, in atomic orbits, or flying freely through a vacuum is irrelevant.

So, any radiation, supposedly coming from so called "dark matter" must STILL be produced by accelerated charges. It is impossible to tell just from the photons produced where these charges were, when they emitted the photons we observe coming to us from distant places in the universe. We can guess where they might have been, in atomic nuclei, in the orbit of atoms or just flying through space, but we cannot know this. It is only a conjecture to try to support a theory.

If in addition to the cosmic background radiation there is also a cosmic electric field or fields, then any charges free in space could be accelerated to enormous energies over the vast distances of the universe. Only a field in the order of a micro-volt per kilometer, could get an electron or other charged particle to the energies we do observe in cosmic rays created by such particles colliding with the atoms of earth's atmosphere. The particles of "solar wind", mostly electrons, appear to be more energetic at greater distances from the sun. This is according to data from space probes. That means they are being accelerated by a weak, but not zero electric field.

Re:-1 physics

[Ambitwistor]

we don't know of any uncharged fundamental matter particles (yet)

Neutrinos?

Re:-1 physics

[drerwk]

I'm looking back into my copy of Baym "Lectures on Quantum Mechanics" in the chapter on Interaction of Radiation with Matter and he says, "Spontaneous emission is just the quantum mechanical version of the classical phenomenon of radiation from an acceleration charge."
Baym later compares the same spontaneous emission work to pair/anti-pair production. I gather that the accelerated charge in the quantum sense corresponds to a change in the expectation value of the momentum of the particle. But, it would take a fair more amount of time to convince myself one way or the other. But it is my understanding that Maxwell is entirely (with minor modifications) compatible with QM which makes me think that I am not that far off.

Re:-1 physics

[drerwk]

You did read what I wrote, right? - I am agreeing that even on a quantum level photon production is sue to charge acceleration.

Re:-1 physics

[Ambitwistor]

I can't see a way in quantum electrodynamics for pair/anti-pair production to be analogous to acceleration radiation. Consider the reverse process, pair annihilation. That can take place even with two particles at relative rest and with zero instantaneous acceleration. The energy of the resulting photon is independent of the particles' accelerations, and is in fact a constant if the particles are at rest.

Classical Maxwellian electromagnetism is compatible with quantum theory since it's the formal classical limit of QED, but that doesn't mean that everything in QED has a classical analogue.

Re:-1 physics

[drerwk]

The positron-electron releases far more energy than the sum of the kinetic energies of the particles unless you get them going REALLY fast. Most of the energy comes from non moving-charge processes.

I do know the difference between mass energy and kinetic energy.

Also note that neutrons and anti-neutrons annihilate. Neither is charged. Yes, they're both composed of charged quarks, but the energy released is far more than the kinetic energy of any of the constituent particles.

I assume you mean the kinetic energy of the N ~N; I am thinking that the motion of the quarks may well be the source of the photon.

It's not particularly insightful to claim that you can't create EM radiation without charged particles since we don't know of any uncharged fundamental matter particles (yet).

I can almost read this to say that Maxwell's equations are not insightful.
They seem to be derivable from QM with a little help from Dirac.
Do tell me what you get when you shake a neutrino.

Re:-1 physics

[drerwk]

Classical Maxwellian electromagnetism is compatible with quantum theory since it's the formal classical limit of QED, but that doesn't mean that everything in QED has a classical analogue.

I can't say otherwise for sure, but I think it might only be one way; that not everything in QM has a classical analogue, but that every classical trait has a QM analogue. Mass, charge, momentum, angular momentum, position... all having QM equivalents.

I actually wish I had the time these days to follow up on what is said in Baym to how far off my thinking is...

Re:-1 physics

[Ambitwistor]

I think it is probably true that everything in classical mechanics has a quantum mechanical analogue, since classical mechanics is just a special case of QM (the hbar->0, decoherent limit).

ah ha!

[Joffy]

Its a cloaked bird of prey's exhaust! FIRE!!!

Little vs. A Little

[phliar]

Perhaps English is not your first language, but "I have little sympathy for fools and Republicans" means that I have no sympathy for them. "I have a little money" means I do have some money, just not a lot.

(Incidentally, there's plenty of evidence for dark matter.)

"Truly" understand?

[phliar]

What does it mean to "truly" understand something? (I would claim that we "truly" understand nothing -- we don't even understand ourselves.)

That's not how science works. You observe reality, you come up with a mathematical model (a hypothesis or theory) that fits the observations, and you test your hypothesis by making predictions and seeing if your hypothesis still looks good. Individual people may say things about what they feel they understand, but not being them, you don't know what their experience of "understanding" is.

GR and QM have been fantastically accurate models, much better than anything else we've ever come up with. Consequences of QM and GR once thought to be outlandish and obviously wrong have been shown to be fact -- repeatedly. That your mind can't admit these concepts means nothing.

why do we have inflation, mommy?

[wikinerd]

Everyone knows very well that dark matter alone is to blame when we face inflation, and printing presses are totally innocent.

Dark thoughts on dark matter.

[mmwithpeanuts]

4% observable, 22% dark matter, 74% dark energy ratio sounds like what some experts say about the usage of our own minds, where only a supposed 10% is applicable. Hm? Perhaps like a seedling in a dark hole, vying for light, we will use 74% dark energy to thrust ourselves through 22% dark matter to sprout into a wonderfully growing entity! How fab! Just like our ten percent brainpower, wading through 90% subconcious, only to find out Freud was somewhat of a fraud. Hm?

YAY

[Friendly Pyro]

Mass Effect is coming true!!!!!!!