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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.
Dark Matter sees evidence of YOU.
Huh?
ZOMG, Mom, is that you?
How amazed would you be to suddenly find that you just forgot what I wrote and you needed to reread my post.... again.
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!!
How amazed would you be to suddenly find that you just forgot what I wrote and you needed to reread my post.... again.
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.
This must be some meaning of 'close' that I was previously unaware of.
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No.
They have an energy dependent signal.
'fucking cookies' are unpleasantly ambiguous.
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where is the dark antimatter?
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.
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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?
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Over there, next to your regular one.
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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.
...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.
All theory is gray
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.
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
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.
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.
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.
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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.
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.
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.
Huh?
No, no, the universe is merely a spheroid region, 705 meters in diameter.
Dude, seriously, read up on electroweak theory. You're so 1960's.
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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'.
Those who advocate genocide deserve every protection afforded by law, and none afforded by common human decency.
It's in my massive muscular physique!
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.
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.
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".
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.
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.
Correct. That's what the article is saying -- it peaks at 650 GeV, and by 800 GeV is indistinguishable from background.