Op donderdag 19 december 2013 09:57:12 UTC+1 schreef Steve Willner:
In article ,

Nicolaas Vroom writes:
But they should demonstrate dark matter based on observations.

The video etc isn't meant to demonstrate dark matter,
They should include a discussion about darkmatter because 85%
of all matter is darkmatter

The matter inferred from galaxy motions should include both
vissible and darkmatter. If there is agreement then there is no
dark matter involved.

The last sentence should be:
If there is agreement between the distribution of observed galaxies
and the distribution of matter inferred from galaxy motions,
then there is no dark matter involved.

The issue is that both visible matter and darkmatter influence the
motion of galaxies. If visible matter agrees with the motions than
there is no darkmatter in the universe. This result should be
discussed in the document, because it is remarkable.

In fact you can go two paths:
1 Based on the observed_motions you can calculate the mass responsible for
these motions and compare this calculated mass with the observed_mass
2 Based on the observed_matter in the universe you can calculate the motions
and compare them with the observed_motions.
This is a very difficult exercise. I tried to do discuss this in
the newsgroup sci.physics.research.
(#1 is also not easy because the distribution of this mass has to be
calculated.
Ofcourse you can assume that the distribution of all mass is identical
as the distribution of visible matter, but that solution is too simple)

That second sentence seems to have an extra "no" in it, but the first
sentence is a misunderstanding. The video shows the _observed_
motions based on observations and with statistical corrections for
galaxies that cannot be observed because they are too faint or are in
the zone of avoidance.
That is correct but I think what you mean are calculated motions.
And IMO these calulations should include darkmatter.

Observed flows towards the Great
Attractor, for example, are larger than can be accounted for by
visible matter in that direction.
This demonstrates my point.
To explain this you need more baryonic or nonbaryonic matter (or both)

Nicolaas Vroom
http://users.pandora.be/nicvroom/