Craig Markwardt wrote:
> Your argument is essentially that of the people requiring dark matter.
> In order to make (nearly) constant galactic rotation velocity
> profiles, the mass enclosed at a radius r must be proportional to r.
> HOWEVER, we can "measure" the amount of mass by looking a the massive
> things which emit radiation: stars (optical & IR light); dust (IR);
> hot plasma (X-rays); cold gas (radio). The conclusions from those
> studies are that the cumulative measureable mass does *not* increase
> linearly with r. Nor is there enough mass to make the rotation speeds
> of ~200 km/s... which leads to the conclusion that there is something
> masive which does *not* emit radiation: dark matter!
All these estimates are made using unproven theoretical assumptions
of how galaxies form and how stars form. These are estimates based
on impossible to prove theoretical assumptions. In fact I argue that
observed rotation curves are proof that galaxy and star formation
theories are incorrect. Anyways, why not measure galaxies mass on
rotation speeds only? Thats how we do it for the solar system.
> A large number of galactic rotation curves have constant portions
> which fall in the range 200 - 300 km/s.
If all galaxies have roughly constant
rotation curves regardless of size and distance from a assumed denser
core Then it must follow that the rotation speeds are not
dependent directly on the mass of the system. If they were,
larger heavier galaxies would spin faster. So obviously your
statement that visible mass cannot account for the faster rotation
speeds is shown to be invalid by the fact that more mass
is observed to not supply faster roation speeds. WITH or
without dark matter.
> No. See above. It is the cross checking of several different methods
> which leads to the requirement for some kind of dark matter.
It seems unscientific that in this `cross checking` process the
only measurement that is truly accurate ( observed speeds) is the
only one that is ignored.
> ???? If you are being serious, you betray your lack of algebraic
> skills necessary for your endeavor.
> > I dont think so. For that matter is M(r/R) the same as
> > M ~ r? I dont think so either as r/R is not the same as r.
> Please. "M ~ r" is common notation to mean "M proportional to r",
> which it clearly is for your "formula." Your inclusion of an
> arbitrary constant R is irrelevant to the discussion.
Why is algebra neccesary for understanding this discussion on
rotation curves? Its an inferior tool compared to what
our brains 3-d visualizing potential offers.
In fact I came up with the same mass distribution
that you agree dark matter uses without ANY algebra used at all.
I only had to visualize and analyse it in my head in a couple of
Not only can I visualize and `measure` anything algebra does,
I can do so with an added time element
You say 1/r^3 is what old einstein worked out
using relativity. He didnt get that from his GR, he tried
out a variety of formulas on top of newtons to see which gave
the results he needed. 1/r^3 is a fairly basic mathemnatical
expression and was probably one of the first he tried.
If Newton had had the available data he would have known that
his formula wasnt sufficient to account for what he saw.
What if he had measured gravity with modern technology?
He would have seen the need for an extra expression
in his formula where gravity also has a falloff described by
1/r^3 and added that in his principia. You dont need any
GR to figure that out.