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Topic: Dark matter found (Read 9480 times)
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Deus Siddis
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I'm not sure I understand that this is "direct proof" Dark Matter is out there, and meets the definition that has been made for it. It sounds like their calculations are off (perhaps because these collision-ers are so distant and so it is just an educated guess what they are made of,) or some unknown force is at work over there. Perhaps its actually Dark Energy, Zero Point Energy, Prauna, The Force, the Uhl, Alien gas miners, etc. 
There's two things from the article that seemed weird to me:
"dark matter, which is invisible and can only be detected through its gravity"
"the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity."
This doesn't sound a lot like dark "matter" to me. But if it is, that last quote proves it is really "Dwarf" Dark Matter! :p
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Death 999
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We did. You did. Yes we can. No.
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Matter is stuff which weighs something even when it is stopped. In other words, it moves slower than the speed of light.
If there is matter which does not have a significant coupling to the electromagnetic, weak, or Strong fields, then it would be nearly interactionless.
This is not at all farfetched -- Neutrons do not have much coupling to the electromagnetic field. Electrons do not have any coupling to the strong field at all. Neutrinos are only coupled to the weak field.
So, it's reasonable to suppose that there is something else which isn't coupled to any of the above. But it would still weigh something.
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Death 999
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On mass vs weight you are correct that there is a difference. However, anything with mass will weigh something, so it works out the same in this case.
Anything with no mass can have no energy unless it is moving at the speed of light, exactly (e.g. photons). A weak exception is granted for particles with extremely short lifetimes (e.g. gluons), as the mass of a particle is constrained to its nominal mass only via resonance. If the particle doesn't last long enough for the resonance to really knock off all the other masses, then it can have a different mass than its nominal mass.
Dark matter would be coupled via gravity at least; there could also be very weak couplings. Like, if they occupy a fourth 'generation' of quarks, they would undergo normal forces, but just not much with our kind of matter. If they are supersymmetric partners, or are nucleonic axions, then they could undergo normal forces with ordinary matter, but only at such high energies that we haven't been able to probe it yet.
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GeomanNL
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I suppose black suns can exist as well then ...
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Death 999
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Our sun is quite typical in that it is black; any other kind of star would be anomalous to the point that it would require new physical theories to explain.
If you're wondering what I'm smoking, keep in mind that black is the condition of having an emissivity of 1 across the spectrum. If the other object is cool, it will appear dark. If the object is hot, it will appear bright.
So, when iron begins to glow red, a physicist would say that it remains black.
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UAF
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Hey that's that "black body radiation" I heard about. Never quite figured it out. Why the "black" in the name?
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Death 999
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Black is the color which absorbs all light, right?
Well, the universe (more or less) has time-reversal symmetry. What's the reverse of absorbing light? Emitting light!
So, black objects are also the best at emitting light.
We do not normally see this because almost everything we see does not emit light itself (at least, not thermally), but instead reflects it. In order for us to see the emitted light of an object, it would have to be hot enough to emit in the visible spectrum, which begins around 500 celsius (around 1000 fahrenheit).
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Kaahtt
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Yeah, I haven't posted in, like, forever. but thats not the point.
Anyway, Dark matter is a misnomer. You see, Scientists don't quite understand that light travels faster away from gravity wells, such as planets, stars, and UrQuan Dreadnaughts.
When taken into account, these pockets of dark matter seem to dissapear
Its just ignorence, really.
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"Life is tough, life is tougher when your stupid"
~John Wayne
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Death 999
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WTF? Scientists don't understand the rules that... scientists... made... oh, wait, that doesn't make any sense at all.
So, do you care to explain the way that galaxies are suspiciously failing to fly apart under ther internal momentum, which is what Dark Matter's job is, mainly
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