Good current paper on mass / luminosity and rotation curves
in [Physics]
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From: John Park on 9 Jul 2010 20:56 dlzc (dlzc1(a)cox.net) writes: > Dear John Park: > > 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. 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. > > 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. --John Park
From: eric gisse on 9 Jul 2010 22:47 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. 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. > 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? > > --John Park
From: Y.Porat on 9 Jul 2010 22:51 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. > > David A. Smith ---------------------- Mr Smith YOU HAVE TO DECIDE ONCE AND FOR ALL WHETHER TH EPHOTON HAS MASS OR NOT OR ELSE YOU CANT MAKE REAL ADVANCE !!! 2 you understood nothing aboutthe Circlon idea !!! IT DOES NOT MOVE IN CIRCLES BECAUSE OF ANY ATTRACTION FORCE !!! IT MOVES IN CIRCLES AS AN CIRCLES BECAUSE 'I WAS BORN LIKE THAT' IOW THAT IS A *BASIC PREMISE*!!! (BASIC ASSUMPTION) as the curved space time is a basic premise th equestion is not if it is reasonable to *you* th ebasic issue is IS IT WORKING OR NOT !!! (while peole started tosuspect that the earth is orbiting the sun it was not written in any book (aactually the oppsite was written in books (:-) so some people made a premise an intuitive guess and only later it has to be found if it has legs or not by accumulating evidence that is how progress in science is done by TRIAL AND ERROR !!! and later some improvement and again another closer trial etc etc (seems that you never did such a thing i ddi things like that and it worked eventually see my model ) so j the Circlon is a by oroduct of my model so see again the circlon at the appendix of my abstarct if right the circlon is not affacted by gravitation!! THE CIRCLON IS **THE MOTHER* OF **ANY* ATTRACTION FORCE !!! see how it can be done in that abstract appendix - and try to understand something revolutionary !!! (not less revoltionary than 'curved space -time' and even better !!! .... it isa done by **mass unknown ( yet) properties -- not by empty space that has no properties by definition !!!) TIA Y.Porat -----------------------------------
From: John Park on 10 Jul 2010 13:36 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. 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. > > 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? >> 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. --John Park
From: Igor on 10 Jul 2010 13:42
On Jul 9, 10:51 pm, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > THE CIRCLON IS **THE MOTHER* OF **ANY* ATTRACTION FORCE !!! > More like the circulon is the child of your ignorance. |