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Dark Matter Paradox / Black Hole Runaway
OK, I'll pose a problem. Time for an Original Post from me ;-)
If, as conjectured, dark matter pervades the Universe, (making up as much as 24% of the mass in the universe) why hasn't/isn't any of this been swallowed into the ultimate gravitational attractor. Why are there so few black holes around and why are they so small if we are awash in "Darth Matter"? Why are they the result only of stellar collapse? Why don't they just form spontaneously out of the Dark Matter aether? David |
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Dark Matter Paradox / Black Hole Runaway
"David Spain" wrote in message m... OK, I'll pose a problem. Time for an Original Post from me ;-) If, as conjectured, dark matter pervades the Universe, (making up as much as 24% of the mass in the universe) why hasn't/isn't any of this been swallowed into the ultimate gravitational attractor. Why are there so few black holes around and why are they so small if we are awash in "Darth Matter"? Why are they the result only of stellar collapse? Why don't they just form spontaneously out of the Dark Matter aether? I'd say because they've never achieved the density required. Even the early lumpiness of the Universe probably didn't provide enough density for dark matter objects to form. If they can't form, no "dark matter stars" no black holes. As for few black holes, not so much. I believe they pretty much believe every galaxy as a decent sized one in the center. David -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net |
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Dark Matter Paradox / Black Hole Runaway
On 2/14/2013 11:06 AM, Greg (Strider) Moore wrote:
"David Spain" wrote in message ... OK, I'll pose a problem. Time for an Original Post from me ;-) If, as conjectured, dark matter pervades the Universe, (making up as much as 24% of the mass in the universe) why hasn't/isn't any of this been swallowed into the ultimate gravitational attractor. Why are there so few black holes around and why are they so small if we are awash in "Darth Matter"? Why are they the result only of stellar collapse? Why don't they just form spontaneously out of the Dark Matter aether? I'd say because they've never achieved the density required. Even the early lumpiness of the Universe probably didn't provide enough density for dark matter objects to form. If they can't form, no "dark matter stars" no black holes. As for few black holes, not so much. I believe they pretty much believe every galaxy as a decent sized one in the center. OK that could explain why we don't see spontaneously forming black holes out of nothing... But if I give the existing ones 24% more mass than was previously considered available why are they size we see? Why are their event horizon diameters pretty much in line with theory that says its due to mass obtained from 'non-dark'? I call this the 'Miami-Beach Theory'. A black hole may have no hair, but as far as dark matter is concerned it must also be wearing sunglasses, and if its name happens to be Kerr, a significant equatorial bulge. In other words a fat, balding 'hole', hanging around the beach with Tequila in hand, with sunglasses on to filter out all the WIMPs leaving them only the ability to see the bikini clad "Material Girls"... Dave |
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Dark Matter Paradox / Black Hole Runaway
Maybe they cannot collide and hence cannot form into huge masses. However,
if that was the case, then what bends the light near where it is said a lot of it exists? Brian -- From the Bed of Brian Gaff. The email is valid as Blind user. "David Spain" wrote in message ... OK, I'll pose a problem. Time for an Original Post from me ;-) If, as conjectured, dark matter pervades the Universe, (making up as much as 24% of the mass in the universe) why hasn't/isn't any of this been swallowed into the ultimate gravitational attractor. Why are there so few black holes around and why are they so small if we are awash in "Darth Matter"? Why are they the result only of stellar collapse? Why don't they just form spontaneously out of the Dark Matter aether? David |
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Dark Matter Paradox / Black Hole Runaway
On Wednesday, February 13, 2013 7:23:32 PM UTC-5, David Spain wrote:
OK, I'll pose a problem. Time for an Original Post from me ;-) If, as conjectured, dark matter pervades the Universe, (making up as much as 24% of the mass in the universe) why hasn't/isn't any of this been swallowed into the ultimate gravitational attractor. Why are there so few black holes around and why are they so small if we are awash in "Darth Matter"? Why are they the result only of stellar collapse? Why don't they just form spontaneously out of the Dark Matter aether? David I am no expert but this is my understanding of the current theory. When regular matter collides part of the kinetic energy in the collision is radiated away as heat (EM radiation) which causes matter to lump together relatively easily. This is due to electromagnetic interactions. Regular mat ter also has other interactions, like the nuclear forces. Unlike regular matter, dark matter is believed to only interact gravitation ally, with itself and also with regular matter; there are no other known in teractions. This means that when two "clouds" of dark matter collide they j ust pass right through each other without any loss of kinetic energy. They may later slow down by gravitational attraction and change direction for an other pass-through. Since there is no mechanism by which kinetic energy can be lost this cycle could go on forever (almost), like an ideal oscillator. This is what prevents dark matter from lumping together. Same happens when dark matter collides with regular matter. Now, since it interacts gravitationally, dark matter should obey General Re lativity, in that it should radiate energy as gravitational waves, and give n a sufficiently long time should slow down and eventually lump together. I can’t give you an estimate for how long that would take, maybe much long er than the age of the Universe. Regarding black holes, I would assume that dark matter falling in should st ay in and add to the mass of the BH, just like regular matter. I don’t th ink there’s a way to tell what proportion of a BH’s mass comes from reg ular or dark matter. But, per above, I don’t think dark matter itself cou ld form a BH that wasn’t there in the first place, unless given a very ve ry long time. |
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Dark Matter Paradox / Black Hole Runaway
As people have said before though, there are problems even obn the level you
state. What started the motion of dark matter in the first place and how can it clump if its so very low in interactablity? I'm loathe to mention it, but since the speed of light appears to be the same in any local frame of reference we can devise, how can anyone tell what is moving in relation to what. there is no centre of the universe, just a horison we cannot see beyond. Thus when talking about that other inconvenient p issue, dark energy, nobody can say there is not a huge enclosure to the universe that as it balloons out does not drag the space within it with it stretching it out. All we see is red shift surely? Brian -- From the Bed of Brian Gaff. The email is valid as Blind user. wrote in message ... On Wednesday, February 13, 2013 7:23:32 PM UTC-5, David Spain wrote: OK, I'll pose a problem. Time for an Original Post from me ;-) If, as conjectured, dark matter pervades the Universe, (making up as much as 24% of the mass in the universe) why hasn't/isn't any of this been swallowed into the ultimate gravitational attractor. Why are there so few black holes around and why are they so small if we are awash in "Darth Matter"? Why are they the result only of stellar collapse? Why don't they just form spontaneously out of the Dark Matter aether? David I am no expert but this is my understanding of the current theory. When regular matter collides part of the kinetic energy in the collision is radiated away as heat (EM radiation) which causes matter to lump together relatively easily. This is due to electromagnetic interactions. Regular mat ter also has other interactions, like the nuclear forces. Unlike regular matter, dark matter is believed to only interact gravitation ally, with itself and also with regular matter; there are no other known in teractions. This means that when two "clouds" of dark matter collide they j ust pass right through each other without any loss of kinetic energy. They may later slow down by gravitational attraction and change direction for an other pass-through. Since there is no mechanism by which kinetic energy can be lost this cycle could go on forever (almost), like an ideal oscillator. This is what prevents dark matter from lumping together. Same happens when dark matter collides with regular matter. Now, since it interacts gravitationally, dark matter should obey General Re lativity, in that it should radiate energy as gravitational waves, and give n a sufficiently long time should slow down and eventually lump together. I can’t give you an estimate for how long that would take, maybe much long er than the age of the Universe. Regarding black holes, I would assume that dark matter falling in should st ay in and add to the mass of the BH, just like regular matter. I don’t th ink there’s a way to tell what proportion of a BH’s mass comes from reg ular or dark matter. But, per above, I don’t think dark matter itself cou ld form a BH that wasn’t there in the first place, unless given a very ve ry long time. |
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Dark Matter Paradox / Black Hole Runaway
Poster ' gave basically the right answer.
In article , "Brian Gaff" writes: What started the motion of dark matter in the first place Gravity. and how can it clump if its so very low in interactablity? Gravity. Look at a globular cluster for example. The stars don't collide or dissipate energy, but the cluster stays bound. I'm oversimplifying a bit, but analysis show the dark matter clumpiness grows over time, and simulations show the same thing. There's a nice movie at http://www.mpa-garching.mpg.de/galform/millennium/ though I fear it won't do much good if you are blind. Basically it shows all the (simulated) dark matter particles zooming around, but they tend to concentrate in overdense regions, and the size of the overdense structures grows with time. I'm loathe to mention it, but since the speed of light appears to be the same in any local frame of reference we can devise, how can anyone tell what is moving in relation to what. It's easy to measure relative motion. There is, so far as we know, no absolute rest frame. there is no centre of the universe, just a horison we cannot see beyond. Right, or at least so we think now. I'm afraid I don't understand the rest of the post, but something outside our horizon shouldn't have any effect on what we observe unless that something was previously in causal contact. Dark energy remains mysterious, but a cosmological constant is certainly one candidate for what it might be. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
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Dark Matter Paradox / Black Hole Runaway
Steve,
I'm not sure I'm buying the 'low density' argument in the vicinity of a black hole. If a BH can form an accretion disk of ordinary matter why is dark matter so selectively able to 'stay away'? Well the day job is getting in the way of doing more research on this topic today. I'll try to follow up with a better reasoned argument when I can find the time to do so. Dave |
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Dark Matter Paradox / Black Hole Runaway
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