md wrote:
"John C. Polasek" wrote in message
...

On Mon, 14 Feb 2005 05:08:56 GMT, "David Nakamoto"
wrote:


One way is to take the measurements in a binary system. From the spectral type
of the component stars, an estimate of their distance, and their orbital period,
all measurable through telescopes and some inferring, you can get the pairs
motion around each other and through space, at least in the line of sight. From
this you can eliminate causes of red shift due to motion, eliminate them, and
uncover other red shift effects.

This was, in fact, how gravitationally induced red shift was measured for the
first time, using the white dwarf companion of Sirius, I believe, if not the one
around Procyon, but I believe it was Sirius. The period, mass, and the pair's
mutual motion through space are measurable or can be calculated from the
observed. From this, all red shifts due to motion can be eliminated. Then
because the companion has a high surface gravity, it can produce a gravitational
red shift, which was what was left when the other causes were eliminated, and it
matched what Einstein predicted for the mass of the companion.

Gravity can be ruled out pretty much because it is a feeble effect.


it would solve some dark matter issues :-) perhaps we have it all wrong and are those galaxies
much heavier than we thought ;-)

Err, that would not solve dark matter issues - that would make them
*bigger*. We can measure with methods independent of Hubble's law for
many galaxies how far away they are. Then we can, using the seen
brightness, estimate how much mass is there. And that visible mass is by
far not enough to account for the observed red shift. So, if the red
shift is due to the gravitation of the galaxy, there has to be a *huge*
amount of non-visible, i.e. dark matter in them!


Bye,
Bjoern