Good current paper on mass / luminosity and rotation curves
in [Physics]
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From: BURT on 10 Jul 2010 15:07 On Jul 9, 10:35 am, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > On Jul 2, 3:48 pm, Sam Wormley <sworml...(a)gmail.com> wrote: > > > > > > > On 6/30/10 12:52 PM, dlzc wrote: > > > >http://arxiv.org/abs/1005.3154 > > > > Provides a lot of background into how Dark Matter is arrived at (as a > > > free parameter, whose spatial distribution is far from simple, > > > depending on the M/L modelled internal to the target galaxy). > > > > David A. Smith > > > David--The case for the existence of dark matter is strong. > > There is copious observational data showing way more gracvitational > > influencve than can be accounted for bu baryonic matter. Background: > > http://en.wikipedia.org/wiki/Dark_matter > > > Quoting from Ned Wright's > > http://www.astro.ucla.edu/~wright/cosmology_faq.html#DM > > > What is the dark matter? > > > "When astronomers add up the masses and luminosities of the stars near > > the Sun, they find that there are about 3 solar masses for every 1 solar > > luminosity. When they measure the total mass of clusters of galaxies and > > compare that to the total luminosity of the clusters, they find about > > 300 solar masses for every solar luminosity. Evidently most of the mass > > in the Universe is dark. If the Universe has the critical density then > > there are about 1000 solar masses for every solar luminosity, so an even > > greater fraction of the Universe is dark matter. But the theory of Big > > Bang nucleosynthesis says that the density of ordinary matter (anything > > made from atoms) can be at most 10% of the critical density, so the > > majority of the Universe does not emit light, does not scatter light, > > does not absorb light, and is not even made out of atoms. It can only be > > "seen" by its gravitational effects. This "non-baryonic" dark matter can > > be neutrinos, if they have small masses instead of being massless, or it > > can be WIMPs (Weakly Interacting Massive Particles), or it could be > > primordial black holes. My nominee for the "least likely to be caught" > > award goes to hypothetical stable Planck mass remnants of primordial > > black holes that have evaporated due to Hawking radiation. The Hawking > > radiation from the not-yet evaporated primordial black holes may be > > detectable by future gamma ray telescopes, but the 20 microgram remnants > > would be very hard to detect". > > ---------------------- > th e mass of the single photon that i found > is about > exp-90 Kilograms > it is based on Plank time emission !!!!! > iow > Black matter might be > th e basic single photons !!! > that at the same time > moves naturally in a closed circle > ie > it can do a double movement > 1 > in a small or big circle > 2 > the center of that circle > moves in addition in a straight line > perpendicular to the plan of that circle -- > (all together a hell ix movement !!!)) > > TIA > Y.Porat > ------------------------------- Hide quoted text - > > - Show quoted text - There is no galactic rotation. There is orbits of stars. Mitch Raemsch
From: eric gisse on 10 Jul 2010 08:22 John Park wrote: > eric gisse (jowr.pi.nospam(a)gmail.com) writes: >> John Park wrote: >> [...] >> >>> I was using electrons as my "particles" and assuming a velocity based on >>> the temperature. >> >> The problem is the 'temperature' can be whatever he wants it to be. All >> that can really be done is produce bounds, and point out there is no >> physical basis for what he's assuming. >> >> Well I guess you could argue that the upper bound for temperature is kT < >> 1/2 m v_esc^2. Probably make further refinements on that based upon >> backscatter, as the energy lost in a collision will be ferocious. > > I realise I don't understand enough about bremsstrahlung--the resulting > energy spectrum for instance. It is proportional to the acceleration felt by the protons/electrons upon collision, but I have no idea how to determine from my current knowledge of particle physics. I do know the acceleration is found to be something absurd like 10^10 gee, though. > > But I just found that with the assumed plasma temperature of 25 > megakelvin, the protons (not even the electrons) have a a thermal speed > almost three times that of the sun's rotation about the galactic centre or > about twice the local escape velocity... > > I think an implicit part of the original argument was that at very high > energies the particle velocities are so great that most collisions won't > change them appreciably--hence no "friction" in the plasma. But you exchange one plead with two more by doing that. 1) What made the hydrogen that way, and why didn't the rest of the visible matter suffer that fate? 2) What's keeping it that way? > >> >> All the change between protons and electrons will do is change energies >> by a factor of 1800. Given the billions of years involved, that's not >> going to change much. >> > Not sure what you're saying here. Doesn't equipartition apply? kT = 1/2 mv^2 Two ensembles with the same thermodynamic temperature will have kinetic energies of the constituent parts that's proportional to the mass. > >>> So far I don't have any reason to revise my estimate of >>> the collision frequency. However, my assumption about the amount of >>> energy radiated away in each collision was glib and looks to be badly >>> wrong. It does seem that such a hot plasma could exist for consderably >>> more than decades--though not, I still suspect, for anything like the >>> age of the galaxy; bremstrahlen, I think, would nibble it away well >>> before then. >> >> It all depends on the initial temperature you assume, and so and and so >> forth. >> >>> > >>>> Yet we have that now. I think you are ignoring the attendant >>>> electrons, and are assuming temperature =3D velocity. Velocity woud >>>> only be constrained by "gravitational binding". >>>> >>>>> And what about the loss of energy as synchrotron >>>>> radiation in the galactic magnetic field? (I suspect a >>>>> time-scale of a few years again, but from a very >>>>> crude estimate.) =A0 >>>> >>> Another bad estimate--the galactic magnetic field appears to be a lot >>> weaker than I had assumed. >> >> It seems to be in the neighborhood of a nanotesla, somewhat more or >> somewhat less depending what you read. What did you assume? >> > A microtesla, until I looked. A bit high. > > --John Park
From: dlzc on 10 Jul 2010 17:09 Dear John Park: On Jul 9, 5:56 pm, af...(a)FreeNet.Carleton.CA (John Park) wrote: > dlzc(dl...(a)cox.net) writes: > > On Jul 9, 10:13=A0am, af...(a)FreeNet.Carleton.CA (John Park) wrote: > >>dlzc(dl...(a)cox.net) writes: > >> > On Jul 8, 3:58=3DA0pm, will...(a)cfa.harvard.edu (Steve Willner) wrote: > >> >> In article <503f477a-1472-4660-a7e7-c33085513...(a)y32g2000prc.googlegro= > > ups=3D > >> > .com>, > >> >> I'm still not clear exactly what distribution you are > >> >> suggesting, but to the extent I understand it (perhaps > >> >> not at all), it looks grossly unstable both gravitationally > >> >> and to its own pressure (given the temperature you > >> >> suggest below). > > >> > I don't see how it is gravitationally unstable, since it > >> > need have essentially no friction. =A0A sea of positive > >> > and negative charges produce no viscosity. =A0And as > >> > to temperature, we know temperatures from ionization > >> > of [minority] members... not so much from the "kinetic > >> > theory of gasses". > > >> Have you tried to estimate a collision frequency for > >> your plasma? For a density of 1 particle per cc and > >> a temperature of 25 x10^6 K I get that an > >> "electromagnetically significant collIsion" > > > ... assuming a velocity, not an ionization state, maybe. > > This stuff is (if it exists) bound to the galaxy. I do > > expect that the stuff that lies in/near the galactic plane > > to be primarily in neutral state, but the stuff that crosses > > the ecliptic not to be. > > >> (i.e. an approach to within a distance comparable to > >> the diameter of a hydrogen atom--so one could expect > >> bremstrahlen or recombination) would happen > >> something like once per week per particle. Such a > >> plasma isn't going to last more than a few decades, let > >> alone the age of the galaxy. > > I was using electrons as my "particles" and assuming a > velocity based on the temperature. The intergalactic and interstellar materials are known (by the heavier elements) to be *ionized* to that temperature, not "moving at that speed". > So far I don't have any reason to revise my estimate of > the collision frequency. However, my assumption about > the amount of energy radiated away in each collision was > glib and looks to be badly wrong. It does seem that such > a hot plasma could exist for consderably more than > decades--though not, I still suspect, for anything like the > age of the galaxy; bremstrahlen, I think, would nibble it > away well before then. Perhaps. But assertions that "we'd certainly see it" are probably false. > >> Yet we have that now. I think you are ignoring the > >> attendant electrons, and are assuming temperature > >> =3D velocity. Velocity [would] only be constrained > >> by "gravitational binding". > > >> And what about the loss of energy as synchrotron > >> radiation in the galactic magnetic field? (I suspect a > >> time-scale of a few years again, but from a very > >> crude estimate.) =A0 > > Another bad estimate--the galactic magnetic field appears > to be a lot weaker than I had assumed. Let's take a little strain off this conversation. Let's say that I expect these gases to be less than 100% of Dark Matter's full complement. In the range of 10 - 20% (for no particular reason). And I don't expect agreement (or at least "well, maybe..."), without someone addressing reionization, or better quantification of the recombination of this plasma. Knowing that someday, someone needs to go from "by gosh and by golly" to some real theory, or its just me p*ssing off a bunch of nice people. Off to do some studying, now that my garbage disposal has been replaced... again. David A. Smith
From: dlzc on 10 Jul 2010 17:14 Dear Y.Porat: On Jul 9, 7:51 pm, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > On Jul 9, 7:48 pm,dlzc<dl...(a)cox.net> wrote: > > > Dear Y.Porat: > > > On Jul 9, 10:23 am, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > > > > On Jun 30, 7:52 pm,dlzc<dl...(a)cox.net> wrote: > > > > >http://arxiv.org/abs/1005.3154 > > > > > Provides a lot of background into how Dark > > > > Matter is arrived at (as a free parameter, > > > > whose spatial distribution is far from > > > > simple, depending on the M/L modelled > > > > internal to the target galaxy). > > > > -------------------- > > > see My 'Circlon'' idea !!! > > > Y.Porat > > > --------------------- > > > Doesn't work, even if light had mass. The mass > > is bound to galaxies, and there is not enough > > gravity to do that far from black holes. > > ---------------------- > YOU HAVE TO DECIDE ONCE AND FOR ALL > WHETHER TH EPHOTON HAS MASS OR NOT > OR ELSE YOU CANT MAKE REAL ADVANCE !!! DO NOT SHOUT. Your circlons still travel at c. They cannot be Dark Matter. That is my total concern. If I were trying to reconcile my utter disdain of Dark Matter, I certainly would not choose a model of light that is obviated by all the other most successful physics theories we have. Hard enough to get people to look at the band-aid that is Dark Matter, without bringing in *your* personal kook-ese. I don't mind kook-ese, as long as I have enough milk. I don't. David A. Smith
From: eric gisse on 10 Jul 2010 18:45
dlzc wrote: [...] > > The intergalactic and interstellar materials are known (by the heavier > elements) to be *ionized* to that temperature, not "moving at that > speed". Learning what temperature means would be abundantly helpful here. [...] |