Dark Matter Discovered Near Solar System? 179
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.
In Soviet Russia (Score:3, Funny)
Dark Matter sees evidence of YOU.
zomg (Score:5, Funny)
ZOMG, Mom, is that you?
Re:zomg (Score:5, Informative)
see http://www.xkcd.com/502/ [xkcd.com] for the joke
close ? (Score:5, Funny)
This must be some meaning of 'close' that I was previously unaware of.
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All things are relative, all relatives are things, my relatives took all my things.
Greg
Close to our Solar System (Score:2)
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 (Score:5, Insightful)
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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 (Score:5, Informative)
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 [wikipedia.org] in diameter. So, it'd be more like finding that random person in the same room.
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Huh?
No, no, the universe is merely a spheroid region, 705 meters in diameter. [wikipedia.org]
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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 [wikipedia.org].
-l
Re:Close to our Solar System (Score:5, Informative)
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.
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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.
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This happened to me - twice! - so I guess the astronomers might have indeed found a lump of dark matter. :-)
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(I forgot about diameter vs. Radius though)
So revising my initial estimate - maybe more like 13ft.
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13.73 billion next Wednesday at 3:54 PM to be precise. ;)
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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
Re:Close to our Solar System (Score:4, Informative)
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 [ucla.edu].
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.
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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.
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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 ;/
the next logical question... (Score:5, Insightful)
where is the dark antimatter?
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It seems that at least some dark matter particles are their own antiparticles since they can annihilate into gamma photons.
Common doublespeak! (Score:5, Insightful)
If this would be the first evidence how can we already have a little evidence of it?
Re:Common doublespeak! (Score:4, Informative)
Re:Common doublespeak! (Score:5, Informative)
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! (Score:5, Informative)
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.
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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 fie
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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 studie
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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
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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.
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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.
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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
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Sheesh. Grow a clue.
"The theory passes numerous observational tests" != "ZOMG science is religion!!1!!".
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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.
Little vs. A Little (Score:2)
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.)
Bad summary. (Score:5, Informative)
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.
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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.
There is no such thing (Score:2, Insightful)
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 f
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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.
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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 su
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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
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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 s
Big whoopie (Score:2)
Big deal. I find dark matter every time I turn out the lights.
This is science?
Correction (Score:2)
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 (Score:3, Funny)
3000 light years??? (Score:2)
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...
why do we have inflation, mommy? (Score:2)
Everyone knows very well that dark matter alone is to blame [arxiv.org] when we face inflation [wikipedia.org], and printing presses [wikipedia.org] are totally innocent.
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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!!
Re:Holy crap. (Score:4, Funny)
'fucking cookies' are unpleasantly ambiguous.
Re:Holy crap. (Score:5, Funny)
Over there, next to your regular one.
Re:math hosers. (Score:5, Informative)
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.
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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
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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.
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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.
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Correct. That's what the article is saying -- it peaks at 650 GeV, and by 800 GeV is indistinguishable from background.
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They have an energy dependent signal.
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...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 guessin
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I think I've seen you make this comment before.
As before, this radiation is not solely produced by charged particles.
Re:math hosers. (Score:4, Insightful)
Dude, seriously, read up on electroweak theory. You're so 1960's.
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...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 i
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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.
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...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 accelera
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...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. (Score:4, Interesting)
http://en.wikipedia.org/wiki/Technetium-99m [wikipedia.org]
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.
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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 pa
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we don't know of any uncharged fundamental matter particles (yet)
Neutrinos?
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....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
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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 classi
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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).
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Uh, annihilation radiation? Radioactive decay? They're pretty well known.
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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.
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. 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. (Score:5, Informative)
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
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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! [wikipedia.org]
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Sure, but Nibbler doesn't care about the math.
rj
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how do you weigh out a pound that weighs ten thousand pound?
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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.
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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.
Re:Kinda Reminds Me of the Face on Mars (Score:5, Insightful)
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.
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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.
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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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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 rant
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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) t
"Truly" understand? (Score:2)
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 experienc
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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.
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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.
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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.
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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 tha
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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.
Well, it is relative (Score:2)
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.
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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.
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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 t
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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.