Does dark matter come in two types?
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From: Yousuf Khan on 24 Jun 2010 02:51 On 6/24/2010 8:14 AM, eric gisse wrote: > Yousuf Khan wrote: > >> On 6/22/2010 2:04 AM, eric gisse wrote: >>> Yousuf Khan wrote: >>>> The universe has precipitated down to all of the physics we see below 1 >>>> TeV, which we now call the Standard Model, because that's all we >>>> encounter in normal life these days. What makes you think that anything >>>> that was created above 1 TeV is stable enough to survive into the >>>> low-energy universe we have now, when everything else has decayed down >>>> to the Standard Model? >>> >>> What makes you think that we see everything? >> >> (1) Because the heavier the particles are, the less stable they are. > > A trend that may or may not continue indefinitely, you do not know. In the search for super-heavy chemical elements, they are trying to get to the "Island of Stability". To get there they know quite a bit about the internal nucleonic valence shells of these elements as they get heavier, and yet they haven't found the Island yet. A lot of careful pre-planning of where to strike the nucleus and what to strike it with goes on. This Island may not exist, as if it actually existed, then one would think that these would've been produced at some point inside supernovas by now. There must be a reason why Uranium is the heaviest naturally occurring element out there. In the search for heavier particles, we don't even know as much as we do about the internal structures of these elements. Yet, you expect it's magically going to stabilize itself? >> The >> heaviest particle we've discovered so far, the Top quark, doesn't even >> last long enough to form Strong force bonds before it decays into >> something else: it's the only quark that's seen alone, not paired up >> with another quark into hadrons of some kind. That's pretty much the >> general case as we go up the mass scale in everything we see. >> >> and, >> >> (2) TeV physics isn't really TeV physics. We're just cranking up >> accelerators to create bigger and bigger junk piles, so we can sort >> through the rubbish to find smaller and smaller pearls. Accelerators >> always had to have more power than the particles they were intended to >> find, but now we have a 7 TeV accelerator (LHC) which is entirely >> devoted to finding a particle, the Higgs, that may end up weighing less >> than 200 GeV, if it's ever found at all. That's a 35:1 signal-to-noise >> ratio. The particles themselves are in the realm of GeV, not TeV. It's >> TeV junk piles to find GeV physics. > > Woah. You clearly don't know what you are talking about with that utterance. You're obviously stumped. Because that response doesn't even rise to your usual level of "pathetic". >>>>> Open a textbook on the subject. GR is not Newton - sign of energy >>>>> matters. Vacuum energy has negative energy density - its' effect is to >>>>> repulse instead of attract. >>>> >>>> The only thing I've seen described as having negative energy is the >>>> vacuum inside Casimir Effect plates, not standard space vacuum. >>> >>> "vacuum" and "vacuum energy" not the same thing. >> >> Read what I said again, negative energy is only inside a Casimir Effect >> vacuum, not a standard vacuum. Until you understand the difference >> between those types of vacuums, the rest of what you say is drivel. > > Once again, reading for comprehension is important. The negative energy > density is there whether or not the plates are. Once again, show your source(s). >>>> What's >>>> your source for negative energy inside a regular vacuum? >>> >>> Vacuum energy. Remember how I mentioned absolute amounts of energy >>> gravitating instead of just the relative amounts like in Newton? >> >> How irrelevant are you trying to be? Newton's laws treat a vacuum as >> having absolutely zero energy. Who mentioned anything about Newton here >> anyways? > > You, implicitly, by pretending energy density doesn't gravitate. You're the only one that came up with that statement. I said nothing about whether energy gravitates or not, one way or another. It's an interesting strategy, create your own argument and attack it yourself. The rest of us are only saying that it's a lack of energy (vacuum energy or otherwise) that is producing the expansion, because space gets a chance to relax in those areas. You're the only one saying vacuum energy is producing the expansion, while at the same time you're saying vacuum energy gravitates; in case it isn't completely obvious to you, energy gravitating and producing an expansion are direct opposite statements. >> What you have to understand is that not all vacuums throughout the >> universe are necessarily the same. Some volumes of vacuums may have more >> energy than others, even if they have the exact same amount of matter >> inside them (i.e. absolutely none). They are affected by their proximity >> to other areas of space where there is lots of matter. The matter >> energizes the closer vacuums, more than the further vacuums. >> >> The entire term "vacuum" only refers to the mass density of a volume of >> space, not its energy density. We'll have to start eventually finding a >> way to measure energy densities separately from mass densities, and >> start referring to "mass vacuums" vs. "energy vacuums" separately. > > Oorrrr we could go with the term 'vacuum' as it is relevant to GR which > happens to mean 'no non-gravitational contributions to the stress tensor'. > Obviously that doesn't touch quantum vacuum. The only reason it doesn't touch quantum vacuum is because we have no way of empirically measuring it. Oh we can come up with a calculation for it, but that's just a best guess average number which we have no way of verifying from region to region. It's not like matter, which you can see and touch, and therefore assign a mass number to it, which thus attaches an energy number to it. If we could actually measure the empirical vacuum energy in intergalactic space, and compare it against the interstellar and interplanetary spaces, it's likely going to be much less in intergalactic space. "Negative energy" is just an energy level less than the local vacuum energy level. Yousuf Khan
From: Yousuf Khan on 24 Jun 2010 03:43 On 6/24/2010 7:28 AM, eric gisse wrote: > Yousuf Khan wrote: > > [...] > >>> Define what dark matter 'should' predict here. >> >> Quite simple really, Dark Matter should predict all of the Dark Matter >> remains attached to only the galaxies in the cluster, it should go >> nowhere else -- ever. > > Wrong. Dark matter will keep going through a shock while the baryonic matter > is slowed down. That's what was seen in the bullet cluster, if you actually > look at the picture. You'll have to be more specific than that. Which baryonic matter? The galaxies or the intergalactic gas? Dark Matter will stay with the galaxies, but it doesn't care if intergalactic gas collides or not. It's not galaxies that are colliding in the Bullet Cluster, it's just gas. Yousuf Khan
From: eric gisse on 25 Jun 2010 21:11 Yousuf Khan wrote: > On 6/24/2010 7:28 AM, eric gisse wrote: >> Yousuf Khan wrote: >> >> [...] >> >>>> Define what dark matter 'should' predict here. >>> >>> Quite simple really, Dark Matter should predict all of the Dark Matter >>> remains attached to only the galaxies in the cluster, it should go >>> nowhere else -- ever. >> >> Wrong. Dark matter will keep going through a shock while the baryonic >> matter is slowed down. That's what was seen in the bullet cluster, if you >> actually look at the picture. > > You'll have to be more specific than that. Which baryonic matter? The > galaxies or the intergalactic gas? Dark Matter will stay with the > galaxies, but it doesn't care if intergalactic gas collides or not. It's > not galaxies that are colliding in the Bullet Cluster, it's just gas. What do you think a cluster merger _is_ ? > > Yousuf Khan
From: eric gisse on 25 Jun 2010 21:40 Yousuf Khan wrote: > On 6/25/2010 8:15 AM, eric gisse wrote: >> Yousuf Khan wrote: >> >> [...] >> >>> >>> In the search for heavier particles, we don't even know as much as we do >>> about the internal structures of these elements. Yet, you expect it's >>> magically going to stabilize itself? >> >> There are particles that are not atoms. Broaden your horizons. > > Atoms are some of the most flexible particles we have been given in > nature. These particles are lower than atoms, they do not exist not as > flexibly. > > Let me put it to you in ways even you should be able to understand. You > can't build a Lego house or a Lego car with a single Lego brick. Atoms > are our Lego houses or Lego cars, these particles are just our Lego > bricks. There are massive, stable particles that are not atoms. I am repeating trivial points because they seem to be not sinking in on your end. > >>>>> (2) TeV physics isn't really TeV physics. We're just cranking up >>>>> accelerators to create bigger and bigger junk piles, so we can sort >>>>> through the rubbish to find smaller and smaller pearls. Accelerators >>>>> always had to have more power than the particles they were intended to >>>>> find, but now we have a 7 TeV accelerator (LHC) which is entirely >>>>> devoted to finding a particle, the Higgs, that may end up weighing >>>>> less than 200 GeV, if it's ever found at all. That's a 35:1 >>>>> signal-to-noise ratio. The particles themselves are in the realm of >>>>> GeV, not TeV. It's TeV junk piles to find GeV physics. >>>> >>>> Woah. You clearly don't know what you are talking about with that >>>> utterance. >>> >>> You're obviously stumped. Because that response doesn't even rise to >>> your usual level of "pathetic". >> >> No, I'm sticking with what I said. Your babble about 'signal to noise >> ratio' is just silly and stunningly ignorant. Ask a particle physicist if >> my assessment is unkind - there are a few around here. > > No honest particle physicist would disagree with anything I've said. I That particular union just leaves behind the group of stupid particle physicists. > bring up the word "honest" very deliberately, to mean those particle > physicists who are not involved in the search for further funding > requests for newer, more powerful accelerators. No, what you say is stupid for a handful of reasons less what I'm not mentioning. 1) higher power accelerators have higher luminosity. look up the term. 2) protons are composite particles. Not all of the {ideal} 7 TeV goes into each fragment. Getting 200 GeV into a single fragment and hoping the one per trillion or whatever frequency of happening happens at the same time is a lot easier to do with better accelerators. 3) you have absolutely no idea what 'signal to noise ratio' means. > > We now have a 7 TeV accelerator at the LHC. Supposedly created entirely > to search for a supposedly sub-200 GeV theoretical particle. What if The accelerator wasn't built just to look for the Higgs. Do some research before spouting. > that particle doesn't show up under 200 GeV? Are they going to keep > looking for it at the same accelerator at higher and higher energy > levels? They will upto a certain point, but at what point will they > decide that they need the next generation 14 TeV accelerator, The collisions are {to be} 14 TeV. 7 + 7 = 14 > to keep > searching for it? The signal-to-noise ratio will just keep growing Stop using the term 'signal to noise'. You do not know what it means. > higher if that particle is never found. Do you keep generating funding > requests for bigger accelerators, or just say the Higgs doesn't exist > and let's get on with the alternative theories for mass generation? > >>>>>>>> Open a textbook on the subject. GR is not Newton - sign of energy >>>>>>>> matters. Vacuum energy has negative energy density - its' effect is >>>>>>>> to repulse instead of attract. >>>>>>> >>>>>>> The only thing I've seen described as having negative energy is the >>>>>>> vacuum inside Casimir Effect plates, not standard space vacuum. >>>>>> >>>>>> "vacuum" and "vacuum energy" not the same thing. >>>>> >>>>> Read what I said again, negative energy is only inside a Casimir >>>>> Effect vacuum, not a standard vacuum. Until you understand the >>>>> difference between those types of vacuums, the rest of what you say is >>>>> drivel. >>>> >>>> Once again, reading for comprehension is important. The negative energy >>>> density is there whether or not the plates are. >>> >>> Once again, show your source(s). >> >> I fail to see why I need to source the combination of two basic facts >> about GR and quantum theory: >> >> 1) There's an energy background that manifests as negative energy density >> between parallel conducting plates. >> 2) Absolute - not relative - amounts of energy gravitate. >> >> Do not argue about which you do not understand. > > Obviously you don't know what you're talking about as you can't produce > any sources to back you up. You're covering your ignorance with posturing. > > And beyond that, your understanding of the cosmological constant as > being "negative energy density" is all wrong anyways. The cosmological > constant is described as caused by positive energy density, with > negative pressure. Here's even a source just for giggles, since it > obviously doesn't stop your posturing. Energy = pressure / c^2 Negative pressure means negative...energy? [snip wrongness] >>> You're the only one saying vacuum energy is producing the expansion, >>> while at the same time you're saying vacuum energy gravitates; in case >>> it isn't completely obvious to you, energy gravitating and producing an >>> expansion are direct opposite statements. > >> http://www.astro.ucla.edu/~wright/cosmo_constant.html > > He said exactly what my previous link said, "it's a positive energy > density, but a negative pressure". http://hyperphysics.phy-astr.gsu.edu/hbase/press.html He mentions a positive _cosmological constant_, which corresponds to _negative_ energy density. The placement on the left hand side of the field equations is relevant. > That's not energy gravitating, that's > energy anti-gravitating. The term gravitation does not mean attraction only. Do not abuse the language. [snip] >> "Local dark matter and dark energy as estimated on a scale of ~1 Mpc in a >> self-consistent way", A. Chernin et.al., A&A 507-1271-1276 >> >> My notes as written, as I don't have A&A in front of me : >> >> "Estimating the mass of the local group to ~10^12 M_sun using >> observations that show the gravitational radius of the system >> 3.1< M< 5.8 x 10^12 M_sun. Consistent with other observations. >> The local value for dark energy is 0.8< rho_local< 3.7 >> rho_global, where rho_global is the global value for dark energy >> density. Dark energy provides a correction to the system's >> effective mass via virial theorem estimates" >> >> So much for your guess. > > It won't convince anyone because that's just an energy *calculation*. In > other words, it's not an actual energy *measurement*. These are > theoretical calculations not empirical measurements. > > It's an impossible task right now to measure actual vacuum energy (even > locally), as we haven't invented the equipment yet. So theoretical > calculations is what we have to live with right now, but don't fool > yourself into thinking that any of those calculations have any basis in > reality. > > Yousuf Khan You didn't even look. Don't draw conclusions from things you did not read and did not make any effort in understanding.
From: Yousuf Khan on 29 Jun 2010 11:36
On 6/26/2010 7:11 AM, eric gisse wrote: > Yousuf Khan wrote: >> You'll have to be more specific than that. Which baryonic matter? The >> galaxies or the intergalactic gas? Dark Matter will stay with the >> galaxies, but it doesn't care if intergalactic gas collides or not. It's >> not galaxies that are colliding in the Bullet Cluster, it's just gas. > > What do you think a cluster merger _is_ ? You're practiced at the art of Straw Man fallacies, you should've been a spin-doctor. But do try stay away from drifting off-topic, especially when the topic was a question posed by you. Yousuf Khan |