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Energy Density CBR vs MW at 1pc vs MOND



 
 
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  #1  
Old October 17th 16, 07:22 AM posted to sci.astro.research
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Default Energy Density CBR vs MW at 1pc vs MOND

MOND is presented as a modification of gravity that kicks in when the
local acceleration reaches a low value.

I'm wondering whether anyone has noted the coincidence of the following
values.............(and as well, whether I've goofed in the calculations
and or the values I'm using)

According to various plots for MW stellar rotation curves, MOND kicks in
at about a radius of R = 1kpc = 3.086E19 m

The best value I have so far found for the number of stars within that
radius is about N = 12.3E9. inside of radius 1kpc

This yields
L = 4.75E36 J/s and a volume for the sphere of
V = 1.23E50 m^3
If I consider the energy released per

dt = 1.0 second (which is the energy flowing outward through a spherical
shell of radius 1kpc), I find the energy density within the radius R,
per second of energy emission, to be

Rho_E MW = L dt / V = 3.86E-14 J/m^3 = 3.86E-14 Pa

The energy density of the CBR is around Rho_E CBR = 4.16E-14 Pa, which
is essentially the same value

In other words, the radius where the energy density of MW emissions per
second matches the energy density of the CBR happens to be at 1kpc,
where the MOND effect kicks in.

So, at least for the MW galaxy, if I've done the math right, MOND kicks
in at the same place where the energy density of light being generated
within the the interior of the MW galaxy, matches the energy density of
the CBR.

Did I do the math right and or are the values I'm using about
reasonable?

Ross

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  #2  
Old October 17th 16, 07:43 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default Energy Density CBR vs MW at 1pc vs MOND

In article ,
writes:

MOND is presented as a modification of gravity that kicks in when the
local acceleration reaches a low value.

I'm wondering whether anyone has noted the coincidence of the following
values.............(and as well, whether I've goofed in the calculations
and or the values I'm using)

According to various plots for MW stellar rotation curves, MOND kicks in
at about a radius of R =3D 1kpc =3D 3.086E19 m


In other words, the radius where the energy density of MW emissions per
second matches the energy density of the CBR happens to be at 1kpc,
where the MOND effect kicks in.

So, at least for the MW galaxy, if I've done the math right, MOND kicks
in at the same place where the energy density of light being generated
within the the interior of the MW galaxy, matches the energy density of
the CBR.


I haven't checked the numbers. As I mentioned before, Hoyle pointed out
that the stellar radiation has about the same total energy as the CMB.
Your calculation is probably a variant of this. There seems to be no
significance to this. (In that sense, it's like the fact that the
angular sizes of the Sun and Moon are the same, allowing the corona to
be seen during a solar eclipse. No-one has come up with any explanation
better than coincidence, although it is less likely than many other
coincidences in astrophysics.)

As you say, MOND "kicks in" at a given acceleration, not distance. OK,
to first order, if another galaxy is smaller (larger) then it will kick
in at a smaller (larger) radius, where the CMB flux will also be smaller
(larger). But galaxies vary in surface brightness. All else being
equal, in a low--surface-brightness galaxy, MOND will kick in at the
same distance, and the CMB flux will be the same, but the stellar flux
of course less.

There are a few coincidences related to MOND, some of which might mean
something, but this doesn't appear to be one of them.
 




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